07-Direct Data Access

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Direct Data Access, Data Binding


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Contenty Direct Data Access

y Data Binding

Muzaffer DOAN - Anadolu University 2


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Important Note!!!y Last week, you learned how to connect to databases

using built-in controls.

y Use them in your applications whenever possible.y If you sure that you need to connect to database

manually, follow the instructions explained in thisclass.



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Direct Data Access Querying1. Create Connection, Command, and DataReader

objects

2. Use the DataReader to retrieve information from thedatabase, and display it in a control

3. Close your connection

4. Send the page to the user



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Updating, Inserting, Deleting1. Create new Connection and Command objects

2. Execute the Commandwith the appropriate SQL

statement



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Direct Data Access with ADO.NET



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ADO.NET Data Provider ClassesSQL Server OleDB (Access)

Connection SqlConnection OleDbConnection

Command SqlCommand OleDbCommandDataReader SqlDataReader OleDbDataReader

DataAdapter SqlDataAdapter OleDbDataAdapter


y

Use OracleConnection, OracleCommand, etc. forOracle data providers

y Use OdbcConnection, OdbcCommand, etc. forODBC data providers


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Namespace Importsy Import following namespaces for SQL Server:

y using System.Data;

y using System.Data.SqlClient;y Import following namespaces for Access:

y using System.Data;

y using System.OleDb;



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Connecting Access DatabaseOleDbConnection conn = new OleDbConnection();

conn.ConnectionString =

@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\Survey.mdb";

conn.Open();

// Database operations will be here...

conn.Close();



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Connecting SQL Server ExpressSqlConnection conn = new SqlConnection();

conn.ConnectionString = @"Data Source=.\SQLEXPRESS;

AttachDbFilename=|DataDirectory|\Survey.mdf;Integrated Security=True;User Instance=True";

conn.Open();

// Database operations will be here...

conn.Close();



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Storing the Connection Stringy Write the connection string into connectionString

section ofweb.config file:

...



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Retrieving the Connection Stringy string connectionString = WebConfigurationManager.

ConnectionStrings["Pubs"].ConnectionString;



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Execute Commandy Command object has several methods starting with

the "Execute" string:y

ExecuteNonQuery(): Used for queries that don'treturn any records (e.g. Update, Insert, Delete queries)

y ExecuteReader(): Used for queries that return one ormore records (e.g. Select query)

y Ex

ecuteScalar(): Used for queries that return one ormore records but this method returns only the firstcolumn of the first row (suitable for obtaining numberof records, maximum value of a column)



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The DataReadery Create a DataReader byExecuteReader method of the

Command object

y

Retrieve the record by the Read() method of theDataReader object

y To retrieve the next record, use Read() method again

y If next record is successfully read, the Read() method

returns truey So, continue reading until the Read() method returns

false



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The DataReaderOleDbConnection conn = new OleDbConnection(

@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=

|DataDirectory|\Survey.mdb");

OleDbCommand cmd = new OleDbCommand("SELECT * FROMUserInfo", conn);

conn.Open();

OleDbDataReader reader = cmd.ExecuteReader();

while (reader.Read())

{

Label1.Text += reader["FirstName"] + "
";

}

reader.Close();

conn.Close();Muzaffer DOAN - Anadolu University 18


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ExecuteScalar ExampleOleDbConnection conn = new OleDbConnection(



OleDbCommand cmd = new OleDbCommand("SELECTMAX(FavoriteNumber) FROM UserInfo", conn);

conn.Open();

int maxfav = (int)cmd.ExecuteScalar();

conn.Close();



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ExecuteNonQuery ExampleOleDbConnection conn = new OleDbConnection(



OleDbCommand cmd = new OleDbCommand("DELETE * FROMUserInfo WHERE UserID=5", conn);

conn.Open();

int affectedRowNumber = cmd.ExecuteNonQuery();

conn.Close();



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Data Bindingy The basic principle of data binding is this: you tell a

control where to find your data and how you want itdisplayed, and the control handles the rest of thedetails.

yASP.NET data binding works in one direction only.Information moves from a data object into a control.Then the data objects are thrown away, and the page is

sent to the client. If the user modifies the data in adata-bound control, your program can update thecorresponding record in the database, but nothinghappens automatically.



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Types of ASP.NET Data Bindingy Single-Value, or "Simple", Data Binding

y Single-value data binding allows you to take a variable, a

property, or an expression and insert it dynamically intoa page

y Single-value binding also helps you create templates forthe rich data controls

y

Repeated-Value, or "List", Bindingy Allows you to display an entire table (or just a singlefield from a table)



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Using Data Bindingy To use single-value binding, you must insert a data

binding expression into the markup in the .aspx file(not the code-behind file).

y To use repeated-value binding, you must set one ormore properties of a data control.

y Once you specify data binding, you need to activate it.You accomplish this task by calling the DataBind()

method of the control.yAlternatively, you can bind the whole page at once by

calling the DataBind() method of the current Pageobject.



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A Simple List Binding ExampleyArrayList fruit = new ArrayList();

y fruit.Add("Kiwi");

y fruit.Add("Mango");y fruit.Add("Blueberry");

y fruit.Add("Apricot");

y fruit.Add("Banana");

y lstItems.DataSource = fruit;

y lstItems.DataBind(); // or

y this.DataBind();



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Referencesy Beginning ASP.NET 3.5 in C# 2008: From Novice to

Professional

y

Visual Studio and MSDN Help


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