Linq to SQL Tutorial Daihoc Com Vn 9643

7/21/2019 Linq to SQL Tutorial Daihoc Com Vn 9643

1/103

Su tm bi:www.daihoc.com.vn

2009

LINQ to SQL TutorialFrom ScottGu blog

o Hi Nam


2/103


LINQ to SQL Tutorial

2


c dch tblog ScottGu-http://weblogs.asp.net/scottgu/default.aspx

Ngi dch: o Hi Namhttp://www.daohainam.com
http://weblogs.asp.net/scottgu/default.aspxhttp://weblogs.asp.net/scottgu/default.aspxhttp://weblogs.asp.net/scottgu/default.aspxhttp://www.daohainam.com/http://www.daohainam.com/http://www.daohainam.com/http://www.daohainam.com/http://weblogs.asp.net/scottgu/default.aspx


3/103



3

Mc lcBi 1: Sdng LINQ to SQL .............................................................................................................................. 6

1. LINQ to SQL l g? .................................................................................................................................. 62. M hnh ha CSDL dng LINQ to SQL: ................................................................................................. 63. Tm hiu lp DataContext ........................................................................................................................ 74. Cc v dLINQ to SQL ........................................................................................................................... 8

a. Ly cc Product tCSDL .................................................................................................................... 8b. Cp nht mt sn phm trong CSDL ................................................................................................... 9c. Chn thm mt phn loi mi v hai sn phm vo CSDL ................................................................. 9d. Xa cc sn phm .............................................................................................................................. 10e. Gi mt thtc .................................................................................................................................. 11f. Ly cc sn phm v phn trang ........................................................................................................ 12

5. Tng kt ................................................................................................................................................. 12Bi 2: nh ngha cc lp m hnh dliu ........................................................................................................ 13

1. To ra mt m hnh dliu LINQ to SQL ............................................................................................. 142. Cc lp thc th..................................................................................................................................... 153. To cc lp thc thtCSDL ............................................................................................................... 154. Cch t tn v ngphp snhiu......................................................................................................... 175. Quan hgia cc thc th...................................................................................................................... 186. Delay/Lazy Loading ............................................................................................................................... 197. Dng cc Stored Procedure .................................................................................................................... 19

Dng SPROCS cp nht/xa,thm dliu ............................................................................................ 218. Tng kt ................................................................................................................................................. 22

Bi 3: Truy vn Csdliu ............................................................................................................................ 231. M hnh ha CSDL Northwind dng LINQ to SQL.............................................................................. 232. Ly cc sn phm ................................................................................................................................... 233.

Trc quan ha cc cu truy vn LINQ to SQL trong trnh gli .......................................................... 25

4. Gn ni cc cu truy vn LINQ to SQL vo cc control LINQ to SQL ................................................ 265. Data Sharping ......................................................................................................................................... 276. Phn trang kt qutruy vn.................................................................................................................... 327. Tng kt ................................................................................................................................................. 34

Bi 4: Cp nht csdliu ............................................................................................................................. 351. CSDL Northwind c m hnh ha dng LINQ to SQL ..................................................................... 35

Change Tracking v DataContext.SubmitChanges() ................................................................................. 362. Cc v dInsert v Delete ...................................................................................................................... 37


4/103



4

a. Thm mt sn phm ........................................................................................................................... 38b. Xa cc sn phm .............................................................................................................................. 38

3. Cp nht thng qua cc quan h............................................................................................................. 384. Transactions ........................................................................................................................................... 405. Kim tra dliu v Business Logic ....................................................................................................... 416. Htrkim tra cc gi trthuc tnh da trn schema ca CSDL ........................................................ 417. Htrty bin vic kim tra gi trcc thuc tnh ................................................................................ 418. Htrty bin vic kim tra tnh hp lca thc th........................................................................... 429. Ty bin cc phng thc kim tra vic thm/xa/sa dliu ............................................................. 4310. Nng cao: Xem danh sch thay i cho Transaction ......................................................................... 4411. Xl cc thay i ng thi vi Optimistic Concurrency: ............................................................... 4512. Dng SPROCs hoc ty bin logic cc cu SQL: .............................................................................. 45

Bi 5: Sdng asp:LinqDataSource .................................................................................................................. 471. ng dng mu m chng ta sxy dng: .............................................................................................. 472. l g v n gip g cho chng ta? ..................................................................... 48

Bc 1: nh ngha m hnh dliu .......................................................................................................... 49Bc 2: To danh sch sn phm .............................................................................................................. 50Bc 3: Bcc ct khng cn thit ........................................................................................................... 54Bc 4: Lc danh sch sn phm .............................................................................................................. 57Bc 5: Thm cc quy tc kim tra logic .................................................................................................. 60

3. Tng kt ................................................................................................................................................. 63Bi 6: Ly dliu dng Stored Procedure ......................................................................................................... 65

1. Dng SPROC hay khng SPROC? l mt vn ...................................................................... 652. Cc bc nh xv gi SPROC dng LINQ to SQL ............................................................................ 663. Cch nh xmt SPROC vo mt DataContext ca LINQ ................................................................... 674. Cch gi SPROC mi c to ............................................................................................................. 685. nh xkiu trvca phng thc SPROC vo mt lp trong m hnh dliu ................................ 696. Xl cc tham sthtc dng OUTPUT ............................................................................................. 727. Xl cc thtc trvnhiu kiu kt qukhc nhau........................................................................... 73

Htrcc hm do ngi dng tnh ngha(UDF) ................................................................................. 758. Tng kt ................................................................................................................................................. 77

Bi 7: Cp nht dliu dng Stored Procedure ................................................................................................. 789. Bc 1: To lp truy xut dliu (cha dng n cc thtc) ............................................................ 78

Thm cc quy tc kim tra dliu vo cc lp m hnh dliu ............................................................... 78Thm phng thc GetCustomer() vo lp DataContext ......................................................................... 80


5/103



5

10. Bc 2: Dng lp truy cp dliu (cha sdng SPROC) .............................................................. 8111. Chmt giy - Ti ngh bi vit ny nh ni vvic dng SPROC cm ???............................... 8212. Cch sdng SPROC thc hin Insert/Update/Delete ................................................................. 8313. Bc 3: Thm mt Order bng cch dng SPROC ........................................................................... 8314. Bc 4: Thc hin cp nht dng SPROC ........................................................................................ 8715. Bc 5: Dng lp DAL ln na ......................................................................................................... 8916. Mt su im ca vic dng SPROC ............................................................................................. 89

Dng cc tham sdng output: .................................................................................................................. 89Sthno nu mt SPROC pht ra mt li? ............................................................................................. 90Ti c thvit code thay v dung ORM designer gi SPROC? ............................................................ 90

17. Tng kt ............................................................................................................................................. 90Bi 8: Thc thi cc biu thc SQL ty bin ....................................................................................................... 91

1. Dng cc cu truy vn SQL ty bin vi LINQ to SQL ........................................................................ 932. Dng ExecuteQuery ............................................................................................................................... 933. Ty bin cc biu thc SQL v theo vt (tracking) cc thao tc cp nht: ............................................ 944. Ty bin cc biu thc SQL vi cc lp ca bn .................................................................................. 955. Ty bin cc cu SQL cho Inserts/Updates/Deletes .............................................................................. 956. Tng kt ................................................................................................................................................. 96

Bi 9: Dng biu thc LINQ ty bin vi .................................................................... 971. Tm tt: dng vi mt mnh where c khai bo .................................... 972. Dng cc skin Selecting vi ........................................................................ 983. Thc hin cc php chiu khi truy vn vi skin Selecting .............................................................. 1014. Tng kt ............................................................................................................................................... 103


6/103



6

Bi 1: S dng LINQ to SQL

y l bi vit u tin trong lot bi c ch LINQ to SQL, cc bi ny s cho bn mt ci nhnkhi qut, gip bn lm quen vi LINQ, mt trong nhng cng ngh mi c trong .NET 3.5.

Lot bi ny c da trn lot Tutorial ca ScottGu (http://weblogs.asp.net/scottgu).

1. LINQ to SQL l g?LINQ to SQL l mt phin bn hin thcha ca O/RM (object relational mapping) c bn trong.NET Framework bn Orcas (nay l .NET 3.5), n cho php bn m hnh ha mt c s d liudng cc lp .NET. Sau bn c th truy vn c s d liu (CSDL) dng LINQ, cng nh cpnht/thm/xa d liu t .

LINQ to SQL h tr y transaction, view v cc stored procedure (SP). N cng cung cp mt

cch d dng thm kh nng kim tra tnh hp l ca d liu v cc quy tc vo trong m hnh dliu ca bn.

2. M hnh ha CSDL dng LINQ to SQL:Visual Studio Orcas tch hp thm mt trnhthit kLINQ to SQL nh mt cng c d dngcho vic m hnh hamt cch trc quancc CSDL dng LINQ to SQL. Bi vit sau si su hnvo cch dng trnh thit k ny(bn cng c thxem onvideo ny xem cch ti to mt mhnh LINQ to SQL).

Bng cch dng trnhthit kLINQ to SQL, ti c th d dng to mt m hnh cho CSDL muNorthwind ging nh di y:
http://weblogs.asp.net/scottguhttp://weblogs.asp.net/scottguhttp://weblogs.asp.net/scottguhttp://weblogs.asp.net/scottgu/archive/2007/01/28/video-using-linq-with-asp-net-in-vs-orcas-part-1.aspxhttp://weblogs.asp.net/scottgu/archive/2007/01/28/video-using-linq-with-asp-net-in-vs-orcas-part-1.aspxhttp://weblogs.asp.net/scottgu/archive/2007/01/28/video-using-linq-with-asp-net-in-vs-orcas-part-1.aspxhttp://weblogs.asp.net/scottgu/archive/2007/01/28/video-using-linq-with-asp-net-in-vs-orcas-part-1.aspxhttp://weblogs.asp.net/scottgu/archive/2007/01/28/video-using-linq-with-asp-net-in-vs-orcas-part-1.aspxhttp://weblogs.asp.net/scottgu/archive/2007/01/28/video-using-linq-with-asp-net-in-vs-orcas-part-1.aspxhttp://weblogs.asp.net/scottgu


7/103



7

M hnh LINQ to SQL trn nh ngha bn lp thc th: Product, Category, Orderv OrderDetail.Cc thuc tnh ca mi lp nh x vo cc ct ca bng tng ng trong CSDL. Mi instance camt lp biu din mt dng trong bng d liu.

Cc mi tn gia bn lp thc th trn biu din quan h gia cc thc th khc nhau, chng cto ra da trn cc mi quan h primary-key/foreign-key trong CSDL. Hng ca mi tn ch ra miquan h l mt mt hay mt nhiu. Cc thuc tnh tng ng s c thm vo cc lp thc thtrong cc trng hp ny. Ly v d, lp Category trn c mt mi quan h mt nhiu vi lpProduct, iu ny c ngha n s c mt thuc tnh Categories l mt tp hp cc i tngProduct trong Category ny. Lp Product cng s c mt thuc tnh Category ch n itngCategory cha Product ny bn trong.

Bngcc phng thcbn tay phibn trong trnh thit k LINQ to SQL trn cha mt danh schcc SP tng tc vi m hnh d liu ca chng ta. Trong v d trn ti thm mt th tc c tn

GetProductsByCategory. N nhn vo mt categoryID v tr v mt chui cc Product. Chng tas xem bng cch no c th gi c th tc ny trong mt on code bn di.

3. Tm hiu lp DataContextKhi bn bm nt Save bn trong mn hnh thit k LINQ to SQL, Visual Studio s lu cc lp.NET biu din cc thc th v quan h bn trong CSDL m chng ta va m hnh ha. C mi mtfile LINQ to SQL chng ta thm vo solution, mt lp DataContext s c to ra, n s c dngkhi cn truy vn hay cp nht li cc thay i. Lp DataContext c to s c cc thuc tnh biudin mi bng c m hnh ha t CSDL, cng nh cc phng thc cho mi SP m chng ta thm vo.


8/103



8

Ly v d, di y l lp NorthwindDataContext c sinh ra da trn m hnh chng ta to ra trn:

4. Cc v dLINQ to SQLMt khi m hnh ha CSDL dng trnh thit k LINQ to SQL, chng ta c th d dng vit ccon lnh lm vic vi n. Di y l mtvi v d v cc thao tc chung khi x l d liu:

a. Ly cc Product tCSDL

on lnh di y dng c php LINQ ly v mt tp IEnumerable cc i tng Product. Ccsn phm c ly ra phi thuc phn loi Beverages:

C#:

VB:


9/103



9

b. Cp nht mt sn phm trong CSDLon lnh di y cho thy cch ly mt sn phm, cp nht li gi tin v lu li CSDL.

C#:

VB:

c. Chn thm mt phn loi mi v hai sn phm vo CSDLon m di y biu din cch to mt phn loi mi, v to hai sn phm mi v a chng votrong phn loi to. C ba sau s c a vo c s d liu.

Ch rng ti khng cn phi t qun l cc mi quan h primary key/foreign key, thay vo , tich n gin thm cc i tng Product vo tp hp Products ca i tng category, v ri thmi tng category vo tp hp Categories ca DataContext, LINQ to SQL s bit cch thit lp ccgi tr primary key/foreign key mt cch thch hp.

(Add c thay i bng InsertOnSubmit trong phin bn hin ti)

C#


10/103



10

VB:

d. Xa cc sn phmon m sau s biu din cch xa tt c cc sn phm Toy khi CSDL:

(RemoveAll c thay i bng DeleteAllOnSubmit trong phin bn hin ti)

C#:


11/103



11

VB:

e. Gi mt thtcon m di y biu din cch ly cc thc th Product m khng dng c php ca LINQ, mgi n th tc GetProductsByCategory chng ta thm vo trc y. Nh rng mt khi ly

v kt qu, ti c th cp nht/xa v sau gi db.SubmitChanges() cp nht cc thay i tr liCSDL.

C#:

VB:


12/103



12

f. Ly cc sn phm v phn trangon m di y biu din cch phn trang trn server nh mt phn ca cu truy vn LINQ. Bngcch dng cc ton t Skip() v Take(), chng ta s ch tr v 10 dng t CSDL bt u t dng200.

C#:

VB:

5. Tng ktLINQ to SQL cung cp mt cch hay, r rng m hnh ha lp d liu trong ng dng ca bn.

Mt khi nh ngha m hinh d liu, bn c th d dng thc hin cc cu truy vn cng nh cpnht, xa, sa d liu mt cch hiu qu.

Hi vng nhng hng dn v v d mutrn gip bn lm quen vi LINQ. Ti s tip tc ccbi vit ny gip bn khm ph LINQ to SQL mt cch chi tit hn.


13/103



13

Bi 2: nh ngha cc lp m hnh d liu

Trongphn mt, ti tho lun v LINQ to SQL l g v cung cp mt ci nhn c bn v nhngtrng hp chng ta c th s dng n.

Trong bi vit u tin, ti cng cung cp cc on code mu biu din cch x l d liu dngLINQ to SQL, bao gm:

Cch truy vn dliu Cc cp nht dliu Cch chn v to quan hcc dng trong mt CSDL Cch xa cc dng trong mt CSDL Cch gi mt thtc Cch ly dliu v phn trang trn server

Ti thc hin tt c cc thao tc d liu bng cch dng mt m hnh d liu LINQ to SQLging nh di y:

Trong bi ny, ti s i vo chi tit cch to ra mt m hnh d liu LINQ to SQL ging nh trn.

LINQ to SQL, cng nh LINQ to SQL, v tt c cc tnh nng khc m ti ni n trong lotbi ny s c coi nh mt phn ca .NET 3.5 v Visual Studio Orcas (nay l Visual Studio2008).

Bn c th lm theo tt c cc bc di y bng cch ti v hocVisual Studio 2008hocVisualWeb Developer Express.C hai u c th c ci t v dng ng thi vi Visual Studio 2005.
http://msdn.microsoft.com/en-us/vstudio/products/aa700831.aspxhttp://msdn.microsoft.com/en-us/vstudio/products/aa700831.aspxhttp://msdn.microsoft.com/en-us/vstudio/products/aa700831.aspxhttp://www.microsoft.com/express/vwd/http://www.microsoft.com/express/vwd/http://www.microsoft.com/express/vwd/http://www.microsoft.com/express/vwd/http://www.microsoft.com/express/vwd/http://www.microsoft.com/express/vwd/http://msdn.microsoft.com/en-us/vstudio/products/aa700831.aspx


14/103



14

1. To ra mt m hnh dliu LINQ to SQLBn c th thm mt m hnh d liu LINQ to SQL v mt d n ASP.NET, Class Library hayWindows bng cch dng ty chn Add New Item bn trong Visual Studio v chn LINQ to

SQL:

Vic chn mc LINQ to SQL s khi chy LINQ to SQL designer, v cho php bn m hnh hacc lp m n biu din mt CSDL quan h. N cng s to ra mtlp kiu DataContext, trong c cc thuc tnh biu din mi bng m chng ta m hnh ha trong CSDL, cng nh cc

phng thc cho mi Stored Procedure m chng ta m hnh ha. Nh ti m t trong phn 1 calot bi ny, lp DataContext l thnh phn trung tm ca m hnh, ton b cc thao tc truy vnhoc cp nht d liu u c thc hin thng qua lp ny.

Diy lnh chp mn hnh ca mt ca s thit k LINQ to SQL, v cng l ci m bn s thyngay khi to ra mt m hnhd liu LINQ to SQL:


15/103



15

2. Cc lp thc thLINQ to SQL cho php bn m hnh ha cc lp nh x vo CSDL. Cc lp ny thng c lEntity Class (lp thc th) v cc instance ca n thng c gi l Entity (thc th). Cc lp

entity nh x vo cc bng bn trong mt CSDL. Cc thuc tnh ca cc lp thng thng nh xvo cc ct trong bng. Mi instance ca mt lp thc th biu din mt dng trong bng.

Cc lp thc th trong LINQ to SQL khng cnphi k tha t mt lp c bit no khc, iu cho php bn c th cho php chng tha k t bt c i tng no bn mun. Tt c cc lp cto ra dng LINQ to SQL designer u c nh ngha nh partial class c ngha l bn c thvit thm code thm vo cc thuc tnh, phng thc v s kin cho chng.

Khng ging nh chc nng DataSet/TableAdapter c trong VS 2005, khi dng LINQ to SQLdesigner, bn khng cn ch ra cu truy vn SQL c dng to ra m hnh v lp truy xut dliu.

Thay vo , bn tp trung ch yu vo vicnh ngha cc lp thc th, cch chngnh x voCSDL, v mi quan hgia chng. Trnh LINQ to SQL c th m bn dng s m bo vic sinh racc lnh SQL thch hp vo lc chy khi bn tng tc v lm vic vi cc thc th d liu. Bn cth dng c php truy vn LINQ ch ra cch bn mun truy vn d liu.

3. To cc lp thc thtCSDLNu ccu trccho CSDL, bn c th dng n to cc lp thc th LINQ to SQL mt cchnhanh chng.


16/103



16

Cc d dng nht lm iu ny l m CSDL trong ca s Server Explorer bn trong VisualStudio, chn cc table v view m bnmun m hnh ha, v ko th chng ln trn ca s LINQ toSQL designer.

Khi bn thm 2 bng (Categories and Products)v 1 view (Invoices) t CSDL Northwind vo cas LINQ to SQL designer, bn s c thm 3 lp thc th c to ra mt cch t ng:


17/103



17

Dng cc lp m hnh ha d liu trn, bn c th chy tt c ccon lnh muc mt t trongphn 1ca lot bi ny. Ti khng cn thm bt k on code no hay cu hnh c th thc hinc cc thao tc query, insert, update, delete v phn trang.

4. Cch t tn v ngphp snhiuMt trong nhng th bn nghe nhc n khi dung LINQ to SQL l n c th t ng chuyn tn

bng v ct thnh dng s nhiu khi to cc lp thc th. Ly v d: Bng Products trong v d cachng ta to ra lp Product, cng nh bng Categories to ra lp Category. Cch t tn nygip m hnh ca bn thng nht vi quy c t tn trong .NET.

Nu khng thch tn lp hay tn thuc tnh do trnh designer sinh ra, bn vn c th sa li thnh btc tn no bn thch. Bn c th lm iu ny bng cch chnh sa tn thc th/thuc tnh bn trongtrnh thit k hoc thng qua bng thuc tnh.

Kh nng t tn cho cc thc th/thuc tnh/quan h khc vi tn trong CSDL rt hu dng trong

mt s trng hp, v d:


18/103



18

1. Khi tn bng/ct trong CSDL b thay i. Bi v m hnh thc th ca bn c th c tn khc vitn trong CSDL, do vy bn c th ch cn cp nht li cc quy tc nh x m khng cn cp nhtchng trnh hoc cc lnh truy vn c th dng c tn mi.

2. Khi cc thnh phn bn trong CSDL c t tn khng r rng. V d: thay v dngau_lnamev au_fnamecho cc tn thuc tnh ca mt lp thc th, bn c th t tn chngthnh LastName v FirstName trong lp thc th v vit cc lnh dng vi n (m khng cni tn cc ct trong CSDL).

5. Quan hgia cc thc thKhi bn ko th cc i tng t Server Explorer ln trn ca s LINQ to SQL designer, VS s tng xc nh cc mi quan h primary key/foreign key gia cc i tng, v t ng to cc quanh mc nhin gia cc lp thcth khc nhau m n to. V d, khi bn thm c hai bngProducts v Categories t Northwind ln trn ca s LINQ to SQL, bn c th thy mi mi quan h

mt nhiu gia chng (c biu din bngmt mi tn trn ca s son tho):

Mi quan h trn s lm lp thc th Product c thm mt thuc tnh l Category, bn c th dng truy cp vo thc th Category ca mt Product. N cng lm lp Category c thm thuc tnhProducts, y l mt tp hp cho php bn ly ra tt c cc Product c trong Category .


19/103



19

Nu bn khng thch cch m trnh thit k m hnh ha hoc t tn, bn hon ton c th chnhsa li. Ch cn click ln mi tn ch ra quan h trn ca s son tho v truy cp vo cc thuc tnhca n thng qua bng thuc tnh i tn, chnh sa hoc thm ch xa n.

6. Delay/Lazy LoadingLINQ to SQL cho php ch ra cc thuc tnh ca mt thc th s c ly v trc(prefetch) hay chc ly khi ngi dng ln u truy cp (gi l delay/lazy loading). Bn c th ty bin cc quy tc

prefetch/lazy load cho cc thuc tnh trong thc th bng cch chn thuc tnh hay quan h , v tli gi tr cho thuc tnh Delay Loaded thnh true hoc false.

Ti c th cu hnh thuc tnh Picture n ch c np khi dng n bng cch t thuc tnhDelay Loaded thnh true:

Ghi ch: Thay v cu hnh prefetch/delay load trn cc thc th, bn cng c th t li thng qua cclnh khi bn thc hin cc cu truy vn LINQ trn lp thc th (ti s hng dn cch lm iuny trong bi vit sau ca lot bi ny).

7. Dng cc Stored ProcedureLINQ to SQL cho php bn c th m hnh ha cc th tc lu tr nh l cc phng thc trong lpDataContext. V d, cho rng chng ta nh ngha m t th tc n gin c tn SPROC nh diy ly v cc thng tin sn phm da trn mt CategoryID:


20/103



20

Ti c th dng Server Explorer trong VS ko/th th tc SPROC ln trn ca s son tho LINQto SQL c th thm mt phng thc cho php goi SPROC. Nu ti th SPROC ln trn thc thProduct, LINQ to SQL designer s khai bo SPROC tr v mt tp kt qu c kiuIEnumerable:

Sau ti c th dng c php LINQ to SQL hay gi thng phng thc trn ly v cc thcth t CSDL:


21/103



21

Dng SPROCS cp nht/xa,thm dliu

Mc nhin LINQ to SQL s t ng to ra cc biu thc SQL ph hp cho bn mi khi mun cpnht/xa/thm d liu. V d, nu bn vit m LINQ to SQL nh di y cp nht mt s gi trtrn mt thc th Product:

Mc nhin, LINQ to SQL s to v thc thi pht biu UPDATE tng ng khi bn xc nhn thay i(ti s ni thm v vn ny trong nhng bi vit khc).

Bn cng c th nh ngha v dng cc th tc INSERT, UPDATE, DELETE nu mun. cuhnh, click ln mt lp thc th trong ca s LINQ to SQL v trong bng thuc tnh, nhn chut lntrn nt trn cc gi tr Delete/Insert/Update, v chn SPROC m bn nh ngha.


22/103



22

C mt iu hay l nhng thay i trn hon ton c thc hin lp nhx LINQ to SQL cngha l tt c nhng on lnh m ti vit trc y u c th tip tc lm vic m khng cnthay i bt k iu g. iu ny gip trnh phi thay i li code ngay c nu sau ny bn mundng mt hm SPROC ti u hn sau ny.

8. Tng ktLINQ to SQL cung cp mt cch thc n gin, sng sa m hnh ha lp d liu trongng dngca bn. Mt khi bnnh ngha m hnhd liu, bn c th thc hin cc cu truy vn, thm, cpnht vxa d liu mt cch d dng v hiu qu.

Dng trnh thit k LINQ to SQL c sn trong Visual Studio v Visual Web Developer Express, bnc th to v qun l m hnh d liu cc k nhanh. Trnh LINQ to SQL designer cng v cng mmdo bn c th ty bin cc hnh vi mc nhin v ghi hoc m rng h thng sao cho ph hpvi nhng yu cu c th no .

Trong nhng bi tip theo ti s dng m hnh d liu chng ta to ra trong bi ny o sauhn vo vic truy vn, thm, cp nht v xa d liu. Trong cc bi vit v cp nht, thm, xa ticng s tho lun v cch thm cc on lnh kim tra d liu cng nh cc quy tc vo cc lpthc th chng ta nh ngha trn.

Mike Taulty cng c mt son videort hay v LINQ to SQL m bn nn xemti y.Chngcung cp mt cch tuyt vi hc bng cch xem nhng ngi khc tng bc s dng LINQ toSQL.
http://mtaulty.com/CommunityServer/blogs/mike_taultys_blog/archive/2007/05/10/9322.aspxhttp://mtaulty.com/CommunityServer/blogs/mike_taultys_blog/archive/2007/05/10/9322.aspxhttp://mtaulty.com/CommunityServer/blogs/mike_taultys_blog/archive/2007/05/10/9322.aspxhttp://mtaulty.com/CommunityServer/blogs/mike_taultys_blog/archive/2007/05/10/9322.aspx


23/103



23

Bi 3: Truy vn Cs d liu

Thng trc ti bt u vit lot biv LINQ to SQL. LINQ to SQL l mt b khung (framework)c sn cho O/RM (object relational mapping) trong .NET 3.5, n cho php bn d dng m hnh ha

cc CSDL quan h dng cc lp .NET. Bn c th dng cc biu thc LINQ truy vn CSDL, cngnh c th cp nht/thm/xa d liu t .

Trong bi vit ny, ti s i su hn vo cch chng ta dng m hnh d liu to trongphn 2,vcch dng n truy vn d liu bn trong mt d n ASP.NET.

1. M hnh ha CSDL Northwind dng LINQ to SQLTrongphn 2ca lot bi ny, ti i qua cc bc to mt m hnh cc lp LINQ to SQL bngcch dng trnh LINQ to SQL c sn trong VS 2008. Di y l mt hnh m ti to dng CSDLmu Northwind:

2. Ly cc sn phmMt khi nh ngha m hnh d liu nh trn, chng ta c th d dng truy vn v ly d liu tCSDL. LINQ to SQL cho phpbn lmiu ny bng cch vit cc cu truy vn dng c phpLINQ vi lpNorthwindDataContext m chng ta to dng trnh thit k LINQ to SQL designer trn.

V d, ly v duyt qua mt tp cc i tng Product, ti c th vit code nh di y:
http://namdh.wordpress.com/2008/11/07/linq-to-sql-part-2-modeling-classes/http://namdh.wordpress.com/2008/11/07/linq-to-sql-part-2-modeling-classes/http://namdh.wordpress.com/2008/11/07/linq-to-sql-part-2-modeling-classes/http://namdh.wordpress.com/2008/11/07/linq-to-sql-part-2-modeling-classes/


24/103



24

Trong cu truy vn trn, ti dng mt mnh where trong c php LINQ ch tr v cc sn

phm trong mt category cho trc. Ti hin ang dng CategoryID ca Product thc hin lc racc dng mong mun.

Mt trong nhng im hay l ti c rt nhiu la chn, rt nhiu cch ty bin cu lnh, v ti cth nm bt u im ca mi quan h gia cc thc th m ti to khi m hnh ha cc lp lmcho cu lnh phong ph v t nhin hn. V d, ti c th sa li cu truy vn lc ra cc dng theoCategoryName thay v CategoryID bng cch vit cu lnh LINQ nh sau:

Ch cch ti dng thuc tnh Category trn mi i tng Product lc theo CategoryNameca Category cha Product . Thuc tnh ny c t ng to ra bi LINQ to SQL v chng ta m hnh ha cc lp Category v Product nh mt mi quan h mt-nhiu.

Mt v d khc v cch dng quan h trong m hnh d liu bn trong cc cu truy vn, chng ta cth vit cu lnh LINQ nh di y ly v ch nhng Product c 5 hoc hn n t hng:

Ch cch chng ta dng tp hp OrderDetails m LINQ to SQL to trn mi lp Product(nh vo mi quan h mt-nhiu m chng ta m hnh ha trong trnh thit k LINQ to SQL).


25/103



25

3. Trc quan ha cc cu truy vn LINQ to SQL trong trnh gliCc trnh nh x O/R (Object relational mapper) nh LINQ to SQL to ra v thc thi cc cu lnhSQL mt cch t ng mi khi bn thc hin mt cu truy vn hay cp nht m hnh i tng ca

n.Mt trong nhng iu quan tm ln nht m cc lp trnh vin mi quen vi ORM l: Cu lnhSQL thc s c thc thi l g?. Mt iu thc s th v v LINQ to SQL l n cho php xem rtd dng cu lnh SQL c thc thi thc s khi bn chyng dngtrong chg li.

Bt u t bn Beta2 ca VS 2008, bn c th dng mt LINQ to SQL visualizer plug-in xem mtcch d dng (v kim tra) bt k cu lnh truy vn LINQ to SQL no. Ch cn t mt breakpoint vdi chut ln trn mt cu lnh LINQ to SQL, sau nhn vo biu tng chic knh lp xem gitr ca cu lnh mt cch trc quan:

Mt ca s s hin ln cho php bnxem mt cch chnh xc cu lnh LINQ to SQL m LINQ toSQL s dng ly v cc i tng Product:

Nu bn nhn nt Execute trn ca s ny, n s cho php bn chy cu lnh SQL trc tip trongtrnh debugger v xem mt cch chnh xc d liu c tr v:


26/103



26

iu ny r rng lm cho vic xem nhng g LINQ to SQL lm cho bn tr thnh cc k d dng.Nh rng bn c th d dng thay th cu SQL m LINQ to SQL thc thi nu mun - mc d trong98% trng hp ti ngh bn s thy rngcu lnhm LINQ to SQL thc thi l thc s, thc s tt.

4. Gn ni cc cu truy vn LINQ to SQL vo cc control LINQ to SQLCc cu truy vn LINQ tr v kt qu m n s implement interrface IEnumerable y cng linterface m cc control ASP.NET dng h tr gn ni cc i tng. iu ny c ngha l bn cth gn ni kt qu ca bt k cu lnh LINQ, LINQ to SQL hay LINQ to XML vo bt k controlASP.NET no.

Ly v d, bn c th khai bo mt control trong mt trang .aspx ging nh sau:

Ti cng c th gn ni kt qu ca cu LINQ to SQL vit trc y vo GridView ging nhsau:


27/103



27

N s sinh ra mt trang trng nh sau:

5. Data SharpingHin ti, mi khixc nh kt qu truyvn, chng ta ly ton b cc ct d liu cn thit cho cc itng thuclp Product:

V d, cu truy vn sau ly v cc sn phm:

V ton b kt qu c tr v:


28/103



28

Thng th chng ta ch mun tr v mt tp con ca d liu v mi sn phm. Chng ta c th dngtnh nngdata shapingm LINQ v cc trnh dich C#, VB mi h tr ch ra rng chng ta chmun mt tp con bng cch chnh sa li cu truy vn nh sau:

iu ny s tr v ch mt tp con d liu c tr v t CSDL:
http://weblogs.asp.net/scottgu/archive/2007/04/21/new-orcas-language-feature-query-syntax.aspxhttp://weblogs.asp.net/scottgu/archive/2007/04/21/new-orcas-language-feature-query-syntax.aspxhttp://weblogs.asp.net/scottgu/archive/2007/04/21/new-orcas-language-feature-query-syntax.aspxhttp://weblogs.asp.net/scottgu/archive/2007/04/21/new-orcas-language-feature-query-syntax.aspx


29/103



29

Mt iu thc s th v v LINQ to SQL l ti c th tn dng tt c u im ca cc quan h trongm hnh d liu khi mun gt gia li d liu. N cho php ti biu din y v hiu qu cc cutruy vn. Ly v d, cu truy vn di y ly v ID v Name t thc th Product, tng s n hng c t cho sn phm , v ri ly tng gi tr ca tng n hng:

LINQ to SQL thng minh c thchuyn biu thc LINQ trn thnh cu SQL di y khin c thc thi:


30/103



30

Cu SQL trn cho php tnh ton tt c cc gi tr ca NumOrders v Revenue t ngay trn SQLserver, v tr v ch nhng d liu nh di y (lm cho vic thc thi c nhanh chng):

Chng ta c th gn ni tp kt qu vo control GridView to ra mt giao din p hn:


31/103



31

Bn cng c th c h tr y bi tnh nng intellisense bn trong VS 2008 khi vit cc cutruy vn LINQ:

Trong v d trn, ti ang s dng mt kiu v danh (anonymous type)v dngobject initialization gt gia v nh ngha cu trc tr v. Mt iu thc s tuyt vi l VS 2008 cung cp intellisensey , kim tra lc dch v c refactoring khi lm vic c vi cc tp kt qu c kiu v danh:
http://weblogs.asp.net/scottgu/archive/2007/05/15/new-orcas-language-feature-anonymous-types.aspx?CommentPosted=truehttp://weblogs.asp.net/scottgu/archive/2007/05/15/new-orcas-language-feature-anonymous-types.aspx?CommentPosted=truehttp://weblogs.asp.net/scottgu/archive/2007/05/15/new-orcas-language-feature-anonymous-types.aspx?CommentPosted=truehttp://weblogs.asp.net/scottgu/archive/2007/03/08/new-c-orcas-language-features-automatic-properties-object-initializers-and-collection-initializers.aspxhttp://weblogs.asp.net/scottgu/archive/2007/03/08/new-c-orcas-language-features-automatic-properties-object-initializers-and-collection-initializers.aspxhttp://weblogs.asp.net/scottgu/archive/2007/03/08/new-c-orcas-language-features-automatic-properties-object-initializers-and-collection-initializers.aspxhttp://weblogs.asp.net/scottgu/archive/2007/03/08/new-c-orcas-language-features-automatic-properties-object-initializers-and-collection-initializers.aspxhttp://weblogs.asp.net/scottgu/archive/2007/05/15/new-orcas-language-feature-anonymous-types.aspx?CommentPosted=true


32/103



32

6. Phn trang kt qutruy vnMt trong nhng yu cu chung khi vit cc trang web l bn phi c kh nng phn trang mt cc hhiu qu. LINQ cung cp sn hai hm m rng cho php bn c th lm iu mt cch d dng vhiu qu hm Skip() v Take().

Bn c th dng Skip() v Take() nh di y ch ra rng bn ch mun ly v 10 i tng snphm bt u t mt sn phm cho trc m chng ta chi ra trong tham s truyn vo:

Ch trnti khng dng Skip() v Take() trong cu khai bo truy vn cc sn phmm chdng ti khi gn kt d liu vo GridView. Mi ngi hay hi C phi lm nh vy th cu lnhu tin s ly ton b d liu t CSDL v lp gia, ri sau mi thc hin vic phn trang ?. Cutr li l Khng. L do l v LINQ ch thc s thc thi cc cu truy vn khi bn ly kt qu t nm thi.


33/103



33

Mt trong nhng u im ca m hnh ny l n cho php bn c th vit cc cu lnh phc tp bngnhiu bc, thay v phi vit trong mt cu lnh n (gip d c hn). N cng cho php bn to racc cu truy vn t cc cu khc, gip bn c th xy dng cc cu truy vn rt phc tp cng nh cth dng li c cc cu truy vn khc.

Mt khi ti c phng thc BindProduct() nh ngha trn, ti c th vit lnh nh di y ly v ch s u t query string, v cho phpdanh sch sn phm c th c hin phn trang vhin th:

N s cho chng ta mt trang hin th cc sn phm c nhiu hn 5 n t hng, cng vi doanh thutng ng, v c phn trang da trn tham s truyn vo qua query string:

Ghi ch: Khi lm vic vi SQL 2005, LINQ to SQL s dng hm ROW_NUMBER() thc hinvic phn trang logic trong CSDL. N m bo rng ch 10 dng d liu c tr v khi chng tathc hin cc cu lnh trn:


34/103



34

N lm cho vic phn trang hiu qu v d dng hn, c bit l vi cc tp d liu ln.

7. Tng ktHi vng cc bc trn cung cp mt ci nhn y v nhng c tnh m LINQ to SQL cungcp, tm hiu thm v cc biu thc LINQ v c php mi c dng trong C# v VB.NET trongVS 2008, xin hy tham kho thm cc bi vit sau:

Automatic Properties, Object Initializer and Collection Initializers Extension Methods Lambda Expressions Query Syntax Anonymous Types

Trong bi vit tip theo trong lot bi ny, ti s cho thy cch thm cc php kim tra vo m hnhd liu ca chng ta, v biu din cch chng ta c th dng a logic chng trnh vo mi lnthc thi cc cu lnh update, insert,hay delete d liu. Ti cng s cho cc bn thy cc tnh nngcao cp hn ca lazy loading v eager loading, cch dng control mi htr vic khai bo databinding trong ASP.NET, cch gii quyt xung t
http://weblogs.asp.net/scottgu/archive/2007/03/08/new-c-orcas-language-features-automatic-properties-object-initializers-and-collection-initializers.aspxhttp://weblogs.asp.net/scottgu/archive/2007/03/08/new-c-orcas-language-features-automatic-properties-object-initializers-and-collection-initializers.aspxhttp://weblogs.asp.net/scottgu/archive/2007/03/13/new-orcas-language-feature-extension-methods.aspxhttp://weblogs.asp.net/scottgu/archive/2007/03/13/new-orcas-language-feature-extension-methods.aspxhttp://weblogs.asp.net/scottgu/archive/2007/04/08/new-orcas-language-feature-lambda-expressions.aspxhttp://weblogs.asp.net/scottgu/archive/2007/04/08/new-orcas-language-feature-lambda-expressions.aspxhttp://weblogs.asp.net/scottgu/archive/2007/04/21/new-orcas-language-feature-query-syntax.aspxhttp://weblogs.asp.net/scottgu/archive/2007/04/21/new-orcas-language-feature-query-syntax.aspxhttp://weblogs.asp.net/scottgu/archive/2007/05/15/new-orcas-language-feature-anonymous-types.aspx?CommentPosted=truehttp://weblogs.asp.net/scottgu/archive/2007/05/15/new-orcas-language-feature-anonymous-types.aspx?CommentPosted=truehttp://weblogs.asp.net/scottgu/archive/2007/05/15/new-orcas-language-feature-anonymous-types.aspx?CommentPosted=truehttp://weblogs.asp.net/scottgu/archive/2007/04/21/new-orcas-language-feature-query-syntax.aspxhttp://weblogs.asp.net/scottgu/archive/2007/04/08/new-orcas-language-feature-lambda-expressions.aspxhttp://weblogs.asp.net/scottgu/archive/2007/03/13/new-orcas-language-feature-extension-methods.aspxhttp://weblogs.asp.net/scottgu/archive/2007/03/08/new-c-orcas-language-features-automatic-properties-object-initializers-and-collection-initializers.aspx


35/103



35

Bi 4: Cp nht cs d liu

Trong bi hm nay, ti s ni r hn v cch chng ta dng CSDL c m hnh ha trc y,v dng n cp nht, chnh sa v xa d liu. Ti cng s cho cc bn thy cc chng ta c th

thm cc quy tc (business rule sau ny tr i ti s nguyn t business rule, v t ny r nghahn) v ty bin cch xc thc tnh hpl ca d liu.

1. CSDL Northwind c m hnh ha dng LINQ to SQLTrongphn 2ca lot bi ny, ti i qua cc bc to nn m hnh cc lp LINQ to SQL dngLINQ to SQL designer c trong VS 2008. Di y l s lp c to cho CSDL mu

Northwind v cng s l m hnh c dng trong bi vit ny:

Khi chng ta nh ngha m hnh d liu dng LINQ to SQL designer nh trn, chng ta nhngha ra 5 lp m hnh: Product, Category, Customer, Order and OrderDetail. Cc thuc tnh cami lp nh x vo cc ct tng ng trong bng d liu. Mi i tng thuc lp thc th s biudin mt dng trong bng CSDL.

Khi nh ngha m hnh d liu, LINQ to SQL designer cng to ra mt lp DataContext cung cpcc cch thc truy vn v cp nht li d liu. Trong m hnh mu chng ta nh ngha trn,

lp ny c t tn l NorthwindDataContext. Lp NorthwindDataContext c cc thuc tnh biu


36/103



36

din cc bng chng ta nh ngha trong CSDL (Products, Categories, Customers, Orders,OrderDetails).

Nh chng ta xem trong phn 3, chng ta cng d dng dng cc biu thc LINQ truy vn vly d liu t CSDL bng cch dng lp NorthwindDataContext. LINQ to SQL sau s t ngdin dch cc biu thc thnh cc cu lnh SQL thch hp thc thi.

V d, chng ta c th vit biu thc LINQ nh di y ly v mt i tng Product n bngcch tm da trn tn sn phm:

Ti cng c th vit thm mt cu truy vn LINQ di y ly v tt c cc sn phm t CSDLm hin ti cha c n t hng, v gi tin nhiu hn $100:

Ch cch ti ang dng OrderDetails kt hp vi mi sn phm nh mt phn ca cu truy vn ch ly v cc sn phm khng c n t hng.

Change Tracking v DataContext.SubmitChanges()

When we perform queries and retrieve objects like the product instances above, LINQ to SQL willby default keep track of any changes or updates we later make to these objects. We can make anynumber of queries and changes we want using a LINQ to SQL DataContext, and these changes willall be tracked together.

Khi chng ta thc hin cc cu truy vn v ly v cc i tng nh i tng product trn, LINQto SQL s mc nhin lu li vt ca cc thao tc thay i hay cp nht m chng ta thc hin trn cci tng (gi l change tracking). Chng ta c th thc hin bao nhiu cu truy vn v thay im chng ta mun bng cch dng LINQ to SQL DataContext, v tt c cc thay i s c luvt li.


37/103



37

Ghi ch: Vic lu vt LINQ to SQL xy ra bn phachng trnhgi, v khng lin quan g nCSDL. C ngha l bn khng h dngti nguyn trn CSDL, hoc bn khng cn ci t thm haythay i bt k th g trn CSDL cho php lm iu ny.

Sau khi cp nht cc i tng chng ta ly t LINQ to SQL, chng ta c th gi phngthcSubmitChanges() trn lp DataContext cp nht li cc thay i ln CSDL. Vic gi

phng thc ny s lm cho LINQ to SQL tnh ton ng v thc thi cc cu lnh SQL ph hp cp nht CSDL.

Ly v d, bn c th vit cu lnh di y cp nht li gi tin v s lng n v cn li casn phm Chai:

Khi ti gi northwind.SubmitChanges() nh trn, LINQ to SQL s xy dng v thc thi mt culnh SQL UPDATE m n s cp nht li hai thuc tnh ca sn phm m chng ta sa li nh trn.

Ti c th vit on lnh di y duyt qua danh sch cc sn phm t ph bin v gi cao, sau t li thuc tnh ReorderLevel = 0:

Khi ti gi northwind.SubmitChanges() nh trn, LINQ to SQL s tnh ton v thc thi mt tp thchhp cc pht biu UPDATE cp nht cc sn phm c thuc tnh ReorderLevel b thay i.

Hy nh l nu gi tr ca cc thuc tnh ca i tng Product khng b thay i bi cu lnh trn,c ngha l bn thn i tng khng b thay i, th LINQto SQL cng s khng thc thi bt k culnh UPDATE no trn i tng . V d, nu n gi ca i tng Chai l 2 v s san

phm cn li l 4, th vic gi SubmitChanges() s chng lm thc thi bt k cu SQL no. Cngvy, ch cc sn phm trong v d th hai c ReorderLevel khng bng 0 mi c cp nht khi giSubmitChanges().

2. Cc v dInsert v DeleteNgoi vic cp nht cc dng c trong CSDL, LINQ to SQL cn cho php bn thm v xa dliu. Bn c th lm c iu ny bng vic thm/bt cc i tng d liu t cc tp hp bng


38/103



38

trong lp DataContext, v sau gi SubmitChanges(). LINQ to SQL s lu vt li cc thao tc ny,v t ng thc thi cu lnh SQL INSERT hay DELETE ph hp khi phng thc SubmitChanges()c gi.

a. Thm mt sn phmBn c th thm mt sn phm mi vo CSDL bng vic to ra mt i tng thuc lp Product,gn cc gi tr thuc tnh, v sau thm n vo tp hp Products ca DataContext:

Khi gi SubmitChanges nh trn, mt dng mi s c thm vo bng Product.

b. Xa cc sn phmCng nh ti ni v vic thm mt sn phm mi bng cch i tng Product vo tp hpProducts ca DataContext, ti cng c th lm mt cch ngc li khi mun xa mt sn phm tCSDL bng cch xa n khi tp hp ny:

(RemoveAll c thay i bng DeleteOnSubmit trong phin bn hin ti)

Ch cch ti ly mt tp hp cc sn phm khng cn c sn xut v cng khng c n thng no bng cch dng mt cu truy vn LINQ, ri sau truyn n cho phng thc Remove Allca tp hp Products trong DataContext. Khi gi SubmitChanges(), tt c cc sn phm s b xakhi CSDL.

3. Cp nht thng qua cc quan hiu lm cho cc trnh ORM nh LINQ to SQL cc k mm d l n cho php chng ta d dng mhnh ha mi quan h gia cc bng trong m hnh d liu. V d, ti c th m hnh ha


39/103



39

miProduct trong mt Category, mi Order cha cc OrderDetails cho tng mc, kt hp ccOrderDetail vi mt Product, v lm cho mi Customer kt hp vi mt tp cc Order. Ti biu din cch xy dng v m hnh ha cc mi quan h trongphn 2ca lot bi ny.

LINQ to SQL cho php ti tn dngc u im ca cc mi quan h trong vic truy vn v cpnht d liu. V d, ti c th vit on lnh di y to mt Product mi v kt hp n vi mtcategory Beverages trong CSDL nhdi y:


Hy ch cch ti thm mt i tng Product vo tp hp Products ca mt Category. N s ch rarng c mt mi quan h gia hai i tng, v lm cho LINQ to SQL t ng duy tr mi quan hforeign-key/primary key gia c hai khi ti gi SubmitChanges.

Mt v d khc cho thy LINQto SQL c th gip qun l quan h gia cc bng nh th no vgip cho vic lp trnh sng sa hn, hy xem mt v d di y khi ti to mt Order mi cho mtkhch hng c. Sau khi t gi tr cho ngy chuyn hng v chi ph cho vic t hng, tis totip 2 mc chi tit trong n t hng ch n cc sn phm m khch hng ang mun mua. Sau, ti s kt hp n t hng vi khch hng, v cp nht cc thay i vo CSDL.
http://namdh.wordpress.com/2008/11/07/linq-to-sql-part-2-modeling-classes/http://namdh.wordpress.com/2008/11/07/linq-to-sql-part-2-modeling-classes/http://namdh.wordpress.com/2008/11/07/linq-to-sql-part-2-modeling-classes/http://namdh.wordpress.com/2008/11/07/linq-to-sql-part-2-modeling-classes/


40/103



40


Nh bn thy, m hnh lp trnh trn cho php thc hin tt c cc cng vic ny mt cch cc ksng sa theo phong cch hng i tng.

4. TransactionsMt transaction (giao dch) l mt dch v c cung cp bi mt CSDL (hoc mt trnh qun l tinguyn khc) m bo rng mt tp cc thao tc c lp s c thc thi nh mt n v duy nht

c ngha l hoc tt c cng thnh cng, hoc cng tht bi. V trong trng hp tht bi, tt c ccthao tc l lm s b hon tc trc khi bt k thao tc no khc c cho php thc hin.

Khi gi SubmitChanges() trnlp DataContext, cc lnh cp nht s lun c thc thi trong cngmt transaction. C ngha l CSDL ca bn s khng bao gi trong mt trng thi khng ton vnnu bn thc thi nhiu culnh hoc tt c cc thao tc bn lm s c lu li, hoc khng c bt

k thay i no.Nu khng c mt transaction ang din ra, DataContext ca LINQ to SQL s t ng bt u mttransaction bov cc thao tc cp nht khi gi SubmitChanges(). Thm vo , LINQ to SQLcn cho php bn t nh ngha v dng i tng TransactionScope ca ring bn. iu ny lmcho vic tch hp cc lnh LINQ to SQL vo cc on m truy cp d liu c d dng hn. Ncng c ngha l bn c th a c cc ti nguyn khng phi ca CSDL vo trong cng transaction.V d: bn c th gi i mt thng ip MSMQ, cp nht h thng file (s dng kh nng h trtransaction cho h thng file), v nhm tt c cc thao tc vo trong cng mt transaction m

bn dng cp nht CSDL dng LINQ to SQL.


41/103



41

5. Kim tra dliu v Business LogicMt trong nhng iu quan trng m cc nh pht trin cn ngh n khi lm vic vi d liu l lmsao kt hp c cc php xc thc d liu v cc quy tc chng trnh (business log ic). LINQ to

SQL cng h tr nhiu cch cc nh pht trin c th d dng tch hp chng vo vi cc m hnhd liu ca h.

LINQ to SQL cho php bn thm kh nng xc thc d liu m khng ph thuc vo cch bn to ram hnh d liu cng nh ngun dliu. iu ny cho php bn c th lp li cc php kim tra nhiu ch khc nhau, v lm cho m lnh sng sa v d bo tr hn rt nhiu.

6. Htrkim tra cc gi trthuc tnh da trn schema ca CSDLKhi nh ngha cc lp m hnh d liu dng LINQ to SQL designer trong VS 2008, chng s mcnhin c gn cc quy tc xc thc da trn cu trc nh ngha trong CSDL.

Kiu d liu ca thuc tnh trong cc lp m hnh d liu s khp vi cc kiu d liu tng ngtrong CSDL. iu ny c ngha l bn sgp li bin dch nu c gng gn mt gi tr kiu booleanv cho mt thuc tnh decimal, hoc nu th p kiu d liu mt cch khng hp l.

Nu mt ct trong CSDL c nh du cho php mang gi tr NULL, khi thuc tnh tng ngtrong m hnh d liu c to bi LINQ to SQL designer cng cho php NULL. Cc ct khng cho

php NULL s t ng a ra cc exception nu bn c gng lu mt i tng c thuc tnh mang gi tr NULL. LINQ to SQL s m bo cc ct nh danh/duy nht khng b trng lp trongCSDL.

Bn c th dng LINQ to SQL designer ghi ln cc quy tc xc thc da trn schema numun, nhng cc quy tc ny s c to ra t ng v bn khng cn lm bt k iu g cho

php chng. LINQ to SQL cng t ng x l cc chui escape, do vy bn khng cn lo lng v liSQL injection.

7. Htrty bin vic kim tra gi trcc thuc tnhVic kim tra d liu da trn cu trc nh ngha trong CSDL rt hu ch, nhng ch c coi nh mc c bn, trong thc t c th bn s gp phi nhng yu cu kim tra phc tp hn nhiu.

Hy xem mt v d trong CSDL Northwind, khi ti nh ngha thuc tnh Phone thuc lp Customerc kiu d liu l nvarchar. Cc nh pht trin dng LINQ to SQL c th vit code ging nh diy cp nht n vimt s phone hp l:

Vn lon code trnc coi l hp lng t gc kiu d liu SQL, v chui trn vn l

mt chui nvarcharmc d c th n khng phi l mt s phone hp l:


42/103



42

trnh vic thm cc s phone kiu nh trn vo CSDL, chngta c th thm mt quy tc kim tratnh hp l vo lp Customer. Thm mt quy tc kim tra thc s n gin. Tt c nhng gchng ta cn lm l thm mt partial class vo v nh ngha phng thc nh di y:

on code trn tn dng u im ca 2c tnh trong LINQ to SQL:

1) Tt c cc lp c to ra u l partial c ngha l nh pht trin c th d dng thm vo ccphng thc, thuc tnh v thm ch c cc s kin (v t chng trong mt file ring bit). iu nylm cho vic thm cc quy tc xc thc v cc hm ph tr vo m hnh d liu v lp DataContextrt d dng. Bn khng cn cu hnh hay vit thm cc code no khc lm c iu ny.

2) LINQ to SQL to sn mt lot cc im m rng trong m hnh d liu v lp DataContext mbn c th dng thm vo cc php kim tra d liu trc v sau khi thc hin cc cng vic.Nhiu trong s ng dng mt c tnh ngn ng mi c gi l partial method c trong VB vC# c trong VS 2008 beta 2. Wes Dyer trong nhm C# c mt bi ni v cch cc partial methodlm victi y.

Trong v d v vic kim tra tnh hp l d liu trn, ti dng phng thc OnPhoneChanging, y

l mt phng thc s c thc thi bt k lc no ngi dng gn li gi tr cho thuc tnh Phonetrn mt i tng Customer. Ti c th dng phng thc ny xc thc gi tr u vo theo btk cch g ti mun (trong v d ny, ti dng mt biu thc chnh quy). Nu gi tr hp l, ti chn gin return v khng lm g c, khi LINQ to SQL s cho l cc gi tr ny l gi tr hp l,ngc li ti c th pht ra mt Exception bn trong phng thc kim tra, v php gn khi skhng c thc hin.

8. Htrty bin vic kim tra tnh hp lca thc thVic kim tra trn tng thuc tnh nh trong cc v d trn rt hu dng khi bn mun kim tra gitr ca tn thuc tnh ring l. Nhng i khi, bn s cn phi kim tra da trn nhiu gi tr ca cc

thuc tnh khc nhau.
http://blogs.msdn.com/wesdyer/archive/2007/05/23/in-case-you-haven-t-heard.aspxhttp://blogs.msdn.com/wesdyer/archive/2007/05/23/in-case-you-haven-t-heard.aspxhttp://blogs.msdn.com/wesdyer/archive/2007/05/23/in-case-you-haven-t-heard.aspxhttp://blogs.msdn.com/wesdyer/archive/2007/05/23/in-case-you-haven-t-heard.aspx


43/103



43

Hy xem v d sau, ti s t gi tr cho 2 thuc tnh OrderDatev RequiredDate:


on lnh trn l hp l nu ch n thun xt t gc ngn ng nhng s l khng c nghakhi bnli mun t ngy khch hng yu cutrc ngy t hng.

Tin vui l t bn LINQ to SQL beta 2, chng ta c th thm vo cc quy tc kim tra cho tngthcth trnh cc li kiu nh trn bng cch thm mt lp partial cho lp Order v hin thc hahm OnValidate(), hm ny s c gi trc khi d liu c a vo CSDL. Bn trong phngthc ny, chng ta c th truy cp v kim tra tt c cc thuc tnh ca lp trong m hnh d liu.

Bn trong phng thc ny, bn c th kim tra gi tr bt k thuc tnh no, v thm ch c th truy

cp (ch c) vo cc i tng lin quan, v c th pht ra mt exception nu c tn ti cc gi trkhng hp l. Bt k mt exception no c pht ra t phng thc OnValidate() s lm cho viccp nht b hy b, v hy b cc thay i trong transaction.

9. Ty bin cc phng thc kim tra vic thm/xa/sa dliuC nhiu lc bn mun thm cc php kim tra khi thm/xa/sa d liu. LINQ to SQL Beta2 cho

php lm iu ny bng cch cho php bn thm vo mt lp partial m rng lp DataContext vsau hin thc ha cc phng thc ty bin cc thao tc thm/xa/sacho cc thc th. Ccthc ny s cthc thit ng khi bn gi SubmitChanges() trn lp DataContext.


44/103



44

Bn c th thm cc php kim tra thch hp vo bn trong cc phng thc v nu d liu hpl, LINQ to SQL s tip tc lu li cc thay i vo CSDL (bng cch gi phng thcExecuteDynamicXYZ ca DataContext).

Mt trong nhng iu th v l cc phng thc ph hp s c gi t ng, khng ph thuc vong cnh m i tng c to/xa/sa. Hy xemv dsau, y ti mun to mt Order mi vkt hp n vi mt Customer c:


Khi ti gi northwind.SubmitChanges() trn, LINQ to SQL s xc nh l n cn lu li mt itng Order, vphng thcInsertOrder s t ng c gi.

10. Nng cao: Xem danh sch thay i cho Transactioni khi bn mun thm cc quy tc kim tra m khng th ch da trn tng thao tc thm/xa/saring l, thay vo bn phi c th duyt qua ton b cc thao tc thc hin trong transaction.


45/103



45

Bt u t bn Beta2 ca .NET 3.5, LINQ to SQL cho php bn truy cp vo danh sch ny bngcch gi phng thc DataContext.GetChangeList(). N s tr v mt i tng ChangeList chacc tp hp cho cc thao tc thm/xa/sa c thc hin.

Mt cch tip cn l bn c th to mt lp tha k t lp DataContext v override phng thcSubmitChanges(). Khi bn c th ly ChangeList() cho thao tc cp nht v thc hin cc phpkim tra cn thit trc khi thc thi:

11. Xl cc thay i ng thi vi Optimistic Concurrency:Mt trong nhng vn m cc nh pht trin phi ngh n trong mi trng a ngi dng l lmth no c th x l cc thao tc cp nht trn cc cng mt tp d liu. V d, cho l c hai ngidng ang cng ly v mt i tng product bn trong mt ng dng, v mt ngi t li gi trcho ReorderLevel l 0, trong khi ngi kia t li l 1. Nu c hai ngi dng u lu li cc thayi vo CSDL, nh pht trin cn cn nhc vic x l tranh chp d liu.

Mt cch tip cn n gin l let the last writer win (ngi cui cng l ngi chin thng) cngha l nhng thay i bi ngi u tin s b thay i m khng bit. V iu ny thng ccoi l mt tri nghim km ci (v khng ng) c ngha ngi dng s cm thy kh s dng.

Mt cch tip cn khc m LINQ to SQL h tr l dng m hnh optimistic concurrency khi LINQ to SQL s t ng xc nh xem gi tr gc trong CSDL b thay i b ngi dng khc

hay cha. LINQ to SQL sau s cung cp mt danh sch cc gi tr b xung t ngi pht trinc th chn gii php x l hoc c th yu cu ngi dng chn mt thao tc no h mun.

Ti s ni v cch dng optimistic concurrency vi LINQ to SQL trong cc bi vit khc.

12. Dng SPROCs hoc ty bin logic cc cu SQL:Mt trong nhng cu hi m cc nh pht trin (v c bit l cc DBA cc nh qun tr CSDL),nhng ngi tng vit cc th tc (SPROC) vi cc cu SQL ty bin thng hi khi nhn thyLINQ to SQL ln u tin l: lm sao ti c th kim sot hon ton cc cu lnh SQL c thcthi bn di ?


46/103



46

Mt tin tt l LINQ to SQL c mt m hnh cc k mm do, n cho php cc nh pht trin c ththay th cc cu lnh caLINQ to SQL bng cc th tcinsert, update, delete m h t nh ngha.

iu thc s th v l bn c th bt u bng cch nh ngha m hnh d liu ca ring bn v LINQ to SQL t thc hin cc thao tc thm/sa/xa. Ri sau bn c th ty bin li m hnh dliu thc hin cc thao tc cp nht vi cc th tc hoc cc cu SQL ca bn m khng phi thayi bt k on lnh no dng m hnh d liu , v cng chngphi thay i bt k quy tc kimtra to trc . iu ny cung cp kh nng ty bin rt ln cho bn khi xy dng ng dng.

Ti cng s ni k hn v cch ty bin m hnh d liu dng cc th tc hay cu lnh SQL trongmt bi vit khc.


47/103



47

Bi 5: S dng asp:LinqDataSource

Trong bi vit ny, ti s khm ph control mi c trong ASP.NET thucphin bn .NET 3.5. Control ny l mt datasource control mi cho ASP.NET (ging

ObjectDataSource v SQLDataSource c trong ASP.NET 2.0) cho php bn khai bo vic gn ktd liu vo m hnh d liu ca LINQ to SQL cc k d dng.

1. ng dng mu m chng ta sxy dng:Chng trnh web chnh sa d liu n gin m ti s xy dng qua cc bc c m t trong biny s l mt chng trnhcho php nhp/chnh sa d liu cho cc sn phm trong mt CSDL:

Chng trnh s h tr ngi dng cc tnh nng sau:

1. Cho php ngi dng lc sn phm theo phn loi.2. Cho php ngi dng sp xp cc sn phm bng cch nhp chut ln tiu ct (Name, Price, Units

In Stock, ).3. Cho php ngi dng phn trang cc sn phm (10 sn phm mi trang).4. Cho php ngi dng chnh sa v cp nht cc chi tit sn phm ngay trn trang.5. Cho php ngi dng xa cc sn phm trong danh sch.

ng dng web ny s c xy dng vi mt m hnh d liu hng i tng dng LINQ to SQL.


48/103



48

Tt c cc quy tc x l v kim tra d liu s c xy dng trong lp d liu m khng phitrong lp giao din. iu ny s m bo rng: 1) mt tp cc quy tc x l ng nht s c dng tt c mi ch trong ng dng, 2) chng ta s phi vit t code m khng cn lp li, v 3) c th ddng chnh sa/thay i cc quy tc x l sau ny m khng cn cp nht li chng nhiu ch khcnhau trong ng dng.

Chng ta cng s tn dng c u im ca vic phn trang/sp xp bn trong LINQ to SQL m bo rng cc c tnh khng c thc hin bn trong lp gia (middle -tier), m s cthc hin trong CSDL (c ngha l ch c 10 sn phm c ly ra trong CSDL ti mt thi im,chng ta s khng ly hng ngn dng ri mi thc hin phn trang hay sp xp trn web server).

2. l g v n gip g cho chng ta?Control l mt ASP.NET control hin thc ha m hnhDataSourceControlc gii thiu trong ASP.NET 2.0. N tng t nh cc control ObjectDataSource v

SqlDataSource, bn c th dng n khai bo vic gn ni d liu gia mt control ASP.NET vimt ngund liu. im khc bit l thay v n gn ni trc tip vo CSDL (nh SqlDataSource)hay vo mt lp (ObjectDataSource), c thit k gn vo mt m hnh dliu LINQ.

Mt trong nhng u im ca vic dng l n tn dng c tnh mm do cacc trnh cung cp LINQ (LINQ provider: nh LINQ to SQL, LINQ to Object). Bn khng cnnh ngha cc phng thc query/insert/update/delete cho ngun d liu gi, thay vo bn cth tr n m hnh d liu ca bn, ch ra bn thc th no bn mun lmvic, ri gn ni n vo mt control Asp.NET v cho php chng lm vic vi nhau.

V d, xy dngmt danh sch c bn cc sn phm cho php lm vic vi cc thc th Producttrong m hnh d liu LINQ to SQL, ti c th khai bo mt th trn trang vtr vo lp datacontext ca LINQ to SQL, v ch ra cc thc th (v d: Products) trong m hnhLINQ to SQL m ti mun gn ni. Ti c th cho mt GridView tr vo n (bng cch t thuctnh DataSourceID) cho php xem cc Product theo dng li:

Khng cn lm thm bt k iu g, ti c th thc thi trang web v c mt danh sch cc Productvi kh nng phn trang cng nh sp xp c tch hp sn. Ti cng c th thm mt ntedit/delete v cho php ngi dng chnh sa d liu. Ti khng cn thm bt k phng thc, nhx cc tham s, hay thm ch vit bt k cu lnh no cho x l cctrng hp hin th v cp nht trn n c th lm vic vi m hnh LINQ to SQL m chng ta chn v thc hin cc thao tc t ng. Khi cp nht, LINQ to SQL s m bo rng cc quy tc x l

v kim tra d liu m ta thm vo m hnh LINQ to SQL (di dngcc phng thc partial)cng s c thc hin trc khi d liu c thc s cp nht vo CSDL.
http://msdn2.microsoft.com/en-us/library/ms227679.aspxhttp://msdn2.microsoft.com/en-us/library/ms227679.aspxhttp://msdn2.microsoft.com/en-us/library/ms227679.aspxhttp://msdn2.microsoft.com/en-us/library/ms227679.aspx


49/103



49

Quan trng:Mt trong nhng im hay ca LINQ hay LINQ to SQL l n khng c thit k ch lm vic vi lp giao din, hay vi mt control c th no nh LinqDataSource. Nh bn thytrong cc bi vit trc ca cng lot bi ny, vit code dng LINQ to SQL cc k sng sa. Bnlun c th vit thm cc m lnh ty bin lm vic trc tip vi m hnh d liu LINQ to SQLnu mun, hay trong mt ng cnh no m khng ph hp dng.

Cc phn di y s m t tng bc to nn ng dng web ti ni trn bng cch dng LINQto SQL v .

Bc 1: nh ngha m hnh dliu

Chng ta s bt u vic to ra ng dng bng cch nh ngha m hnh d liu biu din CSDL.

Ti ni v cch to mt m hnh d liu LINQ to SQL dng trnh son tho c trong VS 2008trong bi 2. Di y l nh chp mn hnh cc lp d liu m ti c th nhanh chng to ra dng

LINQ to SQl designer m hnh ha CSDL Northwind:

Ti s duyt li m hnh ny trong bc 5 khi ti thm mt s quy tc kim tra, nhng trong giai

on u, ti s vn dng n (cha chnh sa) to giao din.


50/103



50

Bc 2: To danh sch sn phm

Chng ta s bt u phn giao din bng cch to mt trang ASP.NET vi mt control v dng CSS nh dng:

Chng ta c th vit code gn ni m hnh d liu vo gridview ny (ging nh ti lm trongphn 3), hoc ti c th lm cch khc l dng control mi gn ni gidviewny vi m hnh d liu.

VS 2008 includes build-in designer support to make it easy to connect up our GridView (or any otherASP.NET server control) to LINQ data. To bind our grid above to the data model we createdearlier, we can switch into design-view, select the GridView, and then select the New Data

Source option within the Choose Data Source: drop-down:

Trnh thit ktrong VS 2008 c sn kh nng h tr lm iu ny mt cch d dng vi GridView(hay bt k control ASP.NET no khc) vod liu LINQ. gn ni, chng ta c th chuyn sangch thit k, chn GridView, v sau chn New Data Source bn trong dang sch ChooseData Source::

Mt hp thoi s hin ln, trong c danh sch cc loi datasource, chn LINQ trong hp thoi nyv t trn cho control m bn mun to:


51/103



51

Trnh thit k s hin th tip cc lp DataContext ca LINQ to SQL m ngdng ca bn c th dngc bao gm c trong cc th vin m bn ang tham chiu ti):

Chng ta mun chn m hnh d liu c to trc y vi trnh thit k LINQ to SQL. Chngta cng s mun chn bng d liu bn trong m hnh d liu m chng ta s coi nh thc th chnh


52/103



52

lm vic vi . Trong v d ny chng ta s chn thc th Products. Chngta cng s nhn vo nt Advanced v cho php vic cp nht cng nh xa d liu:

Khi nhn vo nt Finish trn, VS 2008 s khai bo mt trong trang .aspx,v cp nht tr n n (thng qua thuc tnh DataSourceID).N cng s tngtora cc ct trong Grid d trn cu trc ca thc th Products m chng ta chn:

Chng ta cng c th nhp vo hnh tam gic nh bt ln smart task ca GridView v ch rachng ta mun cho php vic phn trang, sp xp, chnh sa v xa d liu:


53/103



53

Chng ta c th nhn F5 thc thi, v c mt trang hin th danh sch sn phm vi y khnng phn trang cng nh sp xp cc ct:

Chng ta cng c th nhn v cc nt edit hoc delete cp nht li d liu:


54/103



54

Nu nhn vo m ngun ca trang, chng ta s thy cc th ca trang cha ni dung ging nh diy. Th ch n lp DataContext ca LINQ to SQL m ta to trc y,cng nh bng d liu m chng ta mun dng. GridView sau ch n (thng qua DataSourceID) v ch ra nhng ct no s c hin th, tiu ct, cng nh cch spxp s c dng khi tiu ct c chn.

Gi chng ta c mt trang web c bn lm vicvi m hnh d liu LINQ to SQL, chng ta cth tip tc ty bin giao din v hnh vi.

Bc 3: Bcc ct khng cn thit

GridView ca chng ta trn c rt nhiu ct c nh ngha sn, 2 trong s (SupplierID vCategoryID) l cc ct kha ngoi, v vic hin th cc ct ny c v nh khng phi l mt tnghay.

Xa bt cc ct khng cn thit

Chng ta c th bt u vic dn dp giao din bng cch xa i mt s ct khng cn thit. Ti cth lm iu ny bng cch sa m ngun, hay trong ch thit k (nhp chut ln ct mun xa vchn Remove). V d, bn c th b ct Quantity Per Unit di y v chy li ng dng cachng ta c mt giao din sng sa hn:


55/103



55

Nu bn tng dng control trc y v truyn cc tham s cho ccphng thc cp nht, mt trong nhng th khn kh bn bit c l l vic thay i tham s ca ccphng thc cp nht trong TableAdapter khi cc thng s c nhn t lp giao din b thay i.V d: nu chng ta xa mt ct trong bng trn, chng ta li phi chnh sa li TableAdapter n h tr cc phng thc cp nht khng cn ti tham s b xa .

Mt iu hay l vi bn khng cn thc hin cc thay i kiu nh vy. Ch

n gin l thm hoc xa mt ct v chy li chng trnh khng cn lm thm bt c iu gkhc. iu ny lm cho vic thay i giao din web dng d hn nhiu.

Xa cc ct SupplierID v CategoryID

Hin ti, chng ta hin th cc gi tr kha ngoi n cc bng Supplier v Category trong GridView:

iu ny tuy cn thit ng t gc m hnh d liu, nhng li khng mang li gi tr g cho ngidng. Th m chng ta lm l hin th CategoryName v SupplierName, v cung cp mt dang schx xung trong ch Edit cho php ngi dng d dng chn cc gi tr cho SupplierID vCategoryID.

Ti c th thay i GridView hin th Supplier Name v Category Name thay v ID bng victhay th vi mt . Trong TemplateField ny, tic th thm

bt k ni dung no ti mun ty bin li cch hin th ca ct d liu.


56/103



56

Trong on m di y, ti s tn dng cc thuc tnh Supplier v Category trn mi Product, nh ti c th d dng gn ni cc ct Supplier.CompanyName v Category.CategoryName v cc cttng ng trong Grid.

V by gi khi chy ng dng, ti s c danh sch cc Category v Supplier theo tn:

to ra danh sch cho php ngi dng chn cc gi tr ca cc ct Supplier v Category trong ch Edit, u tin ti s thm hai control na vo trang. Ti s cu hnh chng gn ni vi Categories v Suppliers bn trong m hnh d liu LINQ to SQL m ta to trcy:


57/103



57

Ti c th quay tr li cc ct m chng ta to v ty bin giao din Editca chng (bng cch ch ra EditItemTemplate). Chng ta cng s ty bin mi ct c mt danhsch trong ch Edit, v cc gi tr s c ly t cc datasource CategoryDataSource vSupplierDataSource trn, v cc mt lin h ny s l 2 chiu:

V gi, khi ngi dng nhp chut ln Edit trn GridView, chng s c hin th nh mt danhsch Supplier m sn phm ang chn kt hp:

V khi bn bm nt Save, sn phm s c cp nht mt cch ph hp (GridView s dng gi trca dng c chn hin ti trong DropDownList a vo SupplierID).

Bc 4: Lc danh sch sn phm

Thay v hin th tt c cc sn phm trong CSDL, bn c th cp nht phn giao din n thm mtdanh sch cho php ngi dng lc li cc sn phm theo mt phn loi no .


58/103



58

V chng ta thm control tham chiu n Categories vo trang web nytrc y, do vy gi nhng g cn lm ch l to mt dropdownlist trn u trang gn ni vi n.V d:

Khi ti chy trang web ny,ti s c trn u trang mt danh sch cho tt c cc mc phn loi:

Bc cui cng l cu hnh GridView n ch hin th cc sn phm trong phn loi c chn,cch d nht l chn Configure DataSource trong smart task ca GridView:

N s a ti quay tr li ca s thit k m ti dng trong phn u bivit ny. Ti c th chn nt Where trong ca s ny thm mt b lc vo control datasource.Ti c th to ra nhiu b lc nu cn, v ko cc gi tr lc t mt vi ch khc nhau (v d: tquerystring (trn web), t cc gi tr trn form, t cc control khc trn trang):


59/103



59

trn, ti s to b lc cc Products theo CategoryID, v sau ly gi tr ca CategoryID mun lct danh sch m chng ta to trn trang:


60/103



60

Sau khi bm Finish, control trn trang ca chng ta s c cp nht sdng b lc ging nh sau:

V by gi nu thc thi trang web, ngi dng s c th chn mt trong cc phn loi c sn v sau phn trang, sp xp, chnh sa hay xa cc sn phm trong phn loi :

Control s t ng p dng cc b lc LINQ cn thit khi lm vic vi cclp LINQ to SQL ca chng ta m bo rng ch c cc d liu cn thit c ly v t CSDL (vd: trong Grid trn, ch c 3 dng sn phm t trang th hai trong nhm cc sn phm Confection

c ly v).

Bn c th s dng s kin Selecting trn nu mun ty bin cu truy vnLINQ trong on code.

Bc 5: Thm cc quy tc kim tra logic

Nh ti ni n trong phn 4 ca lot bi LINQ to SQL ny, khi chng ta nh ngha m hnh dliu LINQ to SQL, mc nhin chng ta s t ng c mt tp hp cc rng buc trong cc lp mhnh d liu, cc rng buc ny c sinh ra da trn nh ngha trong CSDL. iu ny c ngha lnu bn th nhp mt gi tr null vo cho mt ct mandatory, gn mt string vo cho mt ct s

nguyn, hay t gi tr cho kha ngoi cho mt dng khng tn ti, m hnh LINQ to SQL ca chngta s pht ra mt li v nh vy CSDL c ton vn.

Vic kim tra theo cch ny ch nhm m bo s ton vn mc c bn, d vy, n vn cho huht cc ng dng trong thc t. Chng ta cng c th mong mun thm vo cc quy tc logic mtmc cao hn, cho php kim tra cc quy tc business vo trong cc lp m hnh d liu. Xin cmn LINQ to SQL cho php lm iu ny tht d dng ( xem chi tit, xin c li phn 4).

Mt v d v cc quy tc logic

Ly v d, ngoi nhng quy tc logic c bn, chng ta cn mun m bo rng ngi dng s khngth ngng bn mt loi sn phm nu vn cn sn phm loi trong kho hng.


61/103



61

Nu mt ngi dng nhn nt Save dng trn, chng ta s khng cho php vic thay i c luli v pht ra mt li bo cho ngi dng.

Thm mt quy tc kim tra m hnh d liu

Nu kim tra cc quy tc ny lp giao din th s l khng ph hp, v khi quy tc ny s chc p dng cho chnh ni , v s khng t ng c p dng nu chng ta thm mt trang khccng cho php cp nht Product vo ng dng. Vic phn tn cc quy tc kim tra logic/business volp giao din s lm cho vic bo tr tr nn kh khn khi ng dng tr nn ln v phc tp, v ccthay i/cp nht u cn p dng cc thao tc cn thit nhiu ch khc nhau.

Ni ccoi l ph hp t cc quy tc kim tra ny l trong cc lp m hnh d liu LINQ toSQL m chng ta nh ngha trc y. Nh cp n trong phn 4, tt c cc lp c sinhra bi LINQ to SQL designer u c nh ngha nh cc lp partial n cho php chng ta cth d dng thm vo cc phng thc/s kin/thuc tnh. Cc lp m hnh d liu LINQ to SQL s

t ng gi cc phng thc kim tra m chng ta c th vit ra thc hin vic kim tra theomong mun ring.

V d, ti c th thm mt lp partial vo ng dng hin thc phng thc OnValidate() mLINQ to SQL s gi trc khi lu mt i tng Product vo CSDL. Bn trong phng thc ny tic th thm quy tc sau m bo rng cc sn phm khng th c mt ReOrder Level nu sn

phm ngng bn:

Mt khi thm lp trn vo d n, quy tc business trn s c p dng bt k lc no ngidng dng n m hnh d liu v chnh sa li CSDL. iu ny c p dng cho c vic thm mtsn phm mi, cng nh cp nht li mt sn phm c.

V m chng ta nh ngha trn lm vic vi cc lp m hnh d liu

LINQ to SQL, do vy cc thao tc cp nht/xa/thm u phi qua c php kim tra trn trckhi c p dng vo CSDL. Chng ta khng cn lm thm bt k iu gi lp UI php kim tra


62/103



62

ny c thc hin n s t ng c dng bt k ni no cng nh bt k lc no m hnhLINQ to SQL c dng.

Thm phn kim sot li vo giao din

Mc nhin nu ngi dng nhp vo mt gi tr khng hp l cho UnitsOnOrder/Discontinued voGridView, cc lp LINQ to SQL ca chng ta s sinh ra mt exception. n lt s bt li ny v cung cp mt s kin m ngi s dng c th dng xl li . Nu khng c trnh x l li no c cung cp, khi GridView (hoc mt control khc)gn ni vo s bt li ny v cung cp mt event ngi dng c th x ln. Nu li tip tc khng c ai x l li, khi n s c chuyn n cho Page, v chuyn nhm x l Application_Error() trong file Global.asax nu vn khng c trnh x l li. Cc nh phttrin c th chn bt k ch no trong chui x l ny cung cp mt cch tng tc hp l nhtn ngi dng cui.

i vi ng dng ca chng ta, ni hp l nht n x l cc li cp nht d liu l bt s kinRowUpdatedtrn GridView. S kin ny s c pht ra mi khi mt lnh cp nht c thc hintrn datasource, v chng ta c th truy cp thng tin chi tit ca exception nu vic cp nht khngthnh cng, sau o hin th thng bo thch hp cho ngi dng.

rng trn ti khng h thm bt k hm kim tra no vo lp giao din. Thay v vy, ti s lyv chui thng bo li ca exception pht ra t phn business logic v hin th n cho ngidng.

Ch l ti cng ch ra trn l ti mun GridView vn trong ch Edit khi li xy ra bngcch ngi dng s khng b mt i nhng thay i m h to ra, v c th chnh sa cc gitr h nhp vo v click nt update mt ln na lu li. Chng ta cng c th thm mtcontrol vi ID ErrorMessage bt k ch no m ta mun thng bo li hin ra:

V by gi chng ta s th cp nht Product vi cc gi tr kt hp khng hp l, chng ta s thy

mt thng bo li, nh ngi dng s bit cch sa li cho ph hp:


63/103



63

Mt trong nhng u im khi lm theo cch trn l ti c th thm hay thay i cc quy tc trong mhnh d liu m khng cn chnh sa li code trong lp giao din c th hin th thng bo phhp. Cc quy tc xc thc, v thng bo li tng ng, c th c vit mt ch trong lp m hnhd liu v s c p dng ph hp bt k khi no bn dng n.

3. Tng ktControl cung cp mt cch d dng gn ni bt k control ASP.NET vomt m hnh d liu LINQ to SQL. N cho php cc control dng hin th giao din c th va ly

d liu v t LINQ to SQL, cng nh p dng cc thay i thm/xa/sa vo m hnh d liu.

Trong ng dng trn, chng ta dng LINQ to SQL designer to ra mt m hnh d liu rrng v hng i tng. Chng ta sau thm ba control ASP.NET vo trang (GridView,DropDownList, ErrorMessage Literal), v thm ba control gn ni d liucho Product, Category, v Supplier.


64/103



64

Chng ta sau vit thm 5 dng kim tra d liu trong lp m hnh d liu, v 11 dng tronglp giao din x l li.

Kt qu cui cng l mt ng dng web n gin vi giao din c ty bin cho php ngi dnglc d liu ng theo phn loi, sp xp v phn trang mt cch hiu qu trn danh sch sn phm,chnh sa trc tip thng tin sn phm v cho php lu li cc thay i, v xa cc sn phm t hthng.

Trong bi vit tip theo ca lot bi ny, chng ta s khm ph thm LINQ to SQL bao gm kimsot truy xut ng thi, lazy loading, tha k cc nh x bng, cng nh cch dng cc th tc SQL ty bin.


65/103



65

Bi 6: Ly d liu dng Stored Procedure

Trong bi vit hm nay, ti s cho thy cch chng ta c th dng cc stored procedure (SPROCs) vcc hm do ngi dng nh ngha (UDFs) vi m hnh d liu LINQ to SQL. Bi vit ny s tp

trung ch yu vo cch dng SPROCs truy vn v ly d liu v t CSDL. Trong bi vit k tip,ti s hin th cch bn c th dng cc SPROCs cp nht, thm, xa d liu t CSDL.

1. Dng SPROC hay khng SPROC? l mt vn .Cu hi liu nn dng cc cu SQL ng c sinh ra bi trnh ORM hay dng Stored Procedure khixy dng lp d liu l mt ch khng bao gi kt thc tranh ci gia cc nh pht trin, kin trcs phn mm v cc DBA. Rt nhiu ngi thng minh hn ti nhiu vit v ch ny, v vyti s khng ni thm v vn ny y na.

LINQ to SQL i cng vi .NET 3.5 rt mm do, v c th c dng to cc lp m hnh d

liu,trong cc i tng khng ph thuc vo cu trc CSDL pha di, v c th x l cc phpkim tra logic cng nh xc thc tnh hp l ca d liu m khng ph thuc vo vic d liu sc lu np dng cc cu SQL ng hay thng qua cc SPROCs.

Trong biTruy vn C s d liu (phn3),ti tho lun cch bn c th vit cc biu thc truyvn LINQ cho mt m hnh d liu LINQ to SQL dng on m nh sau:

Khi bn vit cc biu thc LINQ kiu nh vy, LINQ to SQL s thc thi cc cu lnh SQL ng bn c th ly v cc i tng khp vi cu truy vn ca bn.

Nh bn c hc trong bi vit ny, bn cng c th dng cc SPROCs trong CSDL trong lpDataContext, n cung cp mt cch khc ly v cc i tng Products bng cch gi th tc

tng ng:
http://namdh.wordpress.com/2009/05/17/2008/11/21/linq-to-sql-part-3-querying-database/http://namdh.wordpress.com/2009/05/17/2008/11/21/linq-to-sql-part-3-querying-database/http://namdh.wordpress.com/2009/05/17/2008/11/21/linq-to-sql-part-3-querying-database/http://namdh.wordpress.com/2009/05/17/2008/11/21/linq-to-sql-part-3-querying-database/http://namdh.wordpress.com/2009/05/17/2008/11/21/linq-to-sql-part-3-querying-database/


66/103



66

Kh nng ny cho php bn dng c cc cu SQL ng v cc SPROCs vi mt m hnh d liu r

rng, mnh m cng nh cung cp s mm do khi lm vic vi cc d n.

2. Cc bc nh xv gi SPROC dng LINQ to SQLTrong phn 2, ti ni v cch dng LINQ to SQL designer to ra mt m hnh d liu LINQ toSQL nh di y:


67/103



67

ca s trn c cha 2 ca s con, ca s bn tri cho php chng ta nh ngha m hnh d liu snh x vo CSDL, ca s bn phi cho php nh x cc th tc v hm vo i tng DataContext,iu ny cho php chng ta c th thay th cc cu SQL ng trong vic ly d liu v.

3. Cch nh xmt SPROC vo mt DataContext ca LINQ nh x mt SPROC vo lp DataContext, trc tin hy m ca s Server Explorer trong VS2008 v m danh sch cc SPROC trong CSDL:

Bn c th nhy p vo bt k th tc SPROC no trn m v chnh sa chng, v d nhCustOrderHist trong Northwind nh di y:

nh x vo SPROC trn vo DataContext, bn c th ko/th n t ca s Server Explorer lntrn ca s LINQ to SQL designer. Vic ny s lm t ng sinh ra mt th tc trong lpDataContext ca LINQ to SQL nh di y:


68/103



68

Mc nhin tn ca phng thc c to trong lp DataContext s chnh l tn ca SPROC, v kiutr v ca phng thc s l mt kiu c to t ng vi cch t tn theo dng[SprocName]Result. V d: SPROC trn s tr vef mt dy cc i tng c kiuCustOrderHistResult. Chng ta c th i tn ca phng thc nu mun bng cch chn n ridng Property Grid t li tn khc.

4. Cch gi SPROC mi c toKhi hon thnh cc bc trn nh x mt SPROC vo lp DataContext ca chng ta, bn c th gi n mt cch d dng ly d liu v. Tt c nhng g chng ta cn lm l gi phng thcm chng ta nh x trong DataContext ly v mt chui cc i tng v t SPROC:

VB:

C#:


69/103



69

Thm na, thay v lp qua tp kt qu nh trn, ti cng c th gn ni n vo cho mt control hin th ra mn hnh, v d nh ti c th dng :

Khi danh sch cc sn phm c mua b khch hng s c hin th nh sau:

5. nh xkiu trvca phng thc SPROC vo mt lp trong m hnh dliuTrong th tc CustOrderHist trn, th tc tr v mt danh sch d liu bao gm 2 ct:ProductName cha tn v TotalNumber cha s sn phm c t hng trong qu kh. LINQ to

SQL designer s t ng to ra mt lp c tn CustOrderHistResult biu din kt qu ny.


70/103



70

Chng ta cng c th chn cch gn kiu tr v ca th tc cho mt lp c sn trong m hnh dliu, v d mt lp thc th Product hay Order.

V d, cho l chng ta c mt th tc tnGetProductsByCategory trong CSDL tr v thng tin snphm ging nh sau:

Cng nh trc y, ta c th to mt phng thc GetProductsByCategory bn trong lp

DataContext m n s gi th tc ny bng cch ko n vo ca s LINQ to SQL designer. Thay vth n vo mt v tr bt k, chng ta s th n ln trn lp Product m ta to ra sn trn sa sny:

Vic ko mt SPROC v th ln trn mt lp Product s lm cho LINQ to SQL Designer to raphng thc GetProductsByCategory tr v mt danh sch cc i tng c kiu Product:


71/103



71

Mt u im ca vic s dng lp Product nh kiu tr v l LINQ to SQL s t ng qun l ccthay i c to ra trn i tng c tr v ny, ging nh c lm vi cc i tng c trv thng qua cc cu truy vn LINQ. Khi gi SubmitChanges() trn DataContext, nhng thay iny cng s c cp nht tr li CSDL.

V d, bn c th vit on code ging nh di y (dng mt SPROC) v thay i gi ca cc snphm bn trong mt Category no thnh 90% gi tr c:

Khi gi SubmitChanges, n s cp nht li gi ca tt c cc sn phm. hiu thm v cch qun l

cc thay i v cch phng thc SubmitChanges() lm vic, cng nh cc thm cc phng thcxc thc logic d liu, xin mi c li bi 4 trong cng lot bi ny.

Trong bi vit tip theo ca lot bi v LINQ to SQL, ti s hng dn cc bn cch thay th cc culnh SQL ng cho vic INSERT/UPDATE/DELETE bng cc th tc SPROC. V khi thay th nhvy, bn hon ton khng phi thay i g trn cc on lnh trn vic thay i ny hon ton xyra trn m hnh d liu v hon ton trong sut vi cc chng trnh dng n.


72/103



72

6. Xl cc tham sthtc dng OUTPUTLINQ to SQL nh x cc tham s dng OUTPUT ca cc SPROC thnh cc tham bin (dng tkha ref trong C# hoc ByRef trong VB.NET), v vicc tham tr, LINQ to SQL dng cc bin kiu

nullable (dng ? trong C# hay trong VB.NET).V d, th tcGetCustomerDetails sau s nhn vo mtCustomerID nh tham s u vo, v tr vtn cng ty nh mt tham s dng OUTPUT v lch s giao dch nh kt qu truy vn:

Nu bn ko th tc trn th vo lp Order trong LINQ to SQL designer, chng ta c th vit lnhnh sau gi n:

VB:

C#:


73/103



73

Ch th tc trn va tr v mt tp cc i tng Order, ng thi tr v CompanyName thng quamt tham s output.

7. Xl cc thtc trvnhiu kiu kt qukhc nhauKhi mt th tc tr v nhiu kiu kt qu khc nhau, kiu tr v ca phng thc trn lpDataContext khng th c p v mt kiu c th no . V d, th tc di y c th tr v mttp cc sm phm hay lnh t hng ty thuc vo tham s u vo:

LINQ to SQL h tr vic to cc phng thctrgip cho php tr v Product hay Order bng cch

thm mt lp partial NorthwindDataContext vo d n v nh ngha mt phng thc trong lpny (trong v d ny chng ta gi l VariablesShapeSample) gi th tc v tr v mt i tngc kiu IMultipleResult nh trong v d sau:

VB:


74/103



74

C#:

Mt khi thm phng thc ny vo d n, bn c th gi v chuyn v kiu thch hp l Prod ucthoc Order:

VB:


75/103



75

C#:

Htrcc hm do ngi dng tnh ngha (UDF)

Thm vo vic h tr cc cc th tc, LINQ to SQL cn h tr cc hm tr v cc gi tr v hnghoc cc bng kt qu. Mt khi c thm vo lp DataContext nh mt phng thc, bn c thdng cc hm UDF ny trong cu trong cc cu lnh LINQ.

V d, hy xem cc hm UDF n gin c tn MyUpperFunction sau y:


76/103



76

Chng ta c th ko v th n t ca s Server Explorer ln ca s LINQ to SQL Designer thmn vo lp DataContext nh mt phng thc.

Chng ta sau c th dng hm UDF ny ngay bn trong cc biu thc LINQ khi vit cc cu truyvn (ging nh chng ta ang dng trong biu thc Where nh di y):

VB:

C#:

Nu bn dngLINQ to SQL Debug Visualizerm ti vit ti y,bn c th thy cc LINQ toSQL chuyn i cu truy vn trn thnh cu lnh SQL thc thi hm UDF khi chy:
http://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspxhttp://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspxhttp://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspxhttp://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspxhttp://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspxhttp://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspxhttp://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspxhttp://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspx


77/103



77

8. Tng ktLINQ to SQL supports the ability to call Stored Procedures and UDFs wi

Linq to SQL Tutorial Daihoc Com Vn 9643

Documents