2.overview of c#

Overview of C# Basic

Contents

Introduction to C# Programing Structure of C# Create First Program using Console Application Class Data types and Variable Declaration Operators Decision making Statements

if,if else, if elseif,nested if Switch Case ? : (Ternary Operator)

Loops for while do while Foreach

Introduction to C#

Language Created by Anders Hejlsberg (father of Delphi)

The Derivation History can be viewed here: http://www.levenez.com/lang/history.html

Principle Influencing Languages: C++ Delphi Java

C# Designed to be an optimal Windows development language

Family of Languages

C#- The Big Ideas

C# is the first “component oriented” language in the C/C++ family Class Properties Methods Events OOPs

Robust and durable software

Garbage collection No memory leaks and stray pointers

Exceptions Error handling is not an afterthought

Type-safety No uninitialized variables, unsafe casts

Versioning Pervasive versioning considerations in all aspects of

language designNamespace (Packages in Java)

Its worth to note

C# is case sensitive.All statements and expression must end with

a semicolon (;).The program execution starts at the Main

method.Unlike Java, file name could be different from

the class name.

Class,Memebers and Methods

Everything is encapsulated in a classCan have:

member data member methods

Class clsName { modifier dataType varName; modifier returnType methodName (params) {

statements; return returnVal;

} }

Class Constructors

Automatically called when an object is instantiated:

public className(parameters){

statements;}

Single inheritanceMultiple interface implementationClass members

Constants, fields, methods, properties, indexers, events, operators, constructors, destructors

Static and instance members Nested types

Member access public, protected, internal, private

Hello World

using System;namespace Sample{

//Class public class HelloWorld { public HelloWorld() {

Constructor }

//Main method public static void Main(string[] args) { Console.WriteLine("Hello World!");

/* Comments in C# } }

}

Compile & Execute a C# Program

If you are using Visual Studio.Net for compiling and executing C# programs, take the following steps:

Start Visual Studio. On the menu bar, choose File, New, Project. Choose Visual C# from templates, and then choose Windows. Choose Console Application. Specify a name for your project, and then choose the OK

button. The new project appears in Solution Explorer. Write code in the Code Editor. Click the Run button or the F5 key to run the project. A

Command Prompt window appears that contains the line Hello World.

Data types and Variable Declaration

Value types Directly contain data Cannot be null

Reference types Contain references to objects May be null

int i = 123; string s = "Hello world";

123i

s "Hello world"

Type System

Value types Primitives int i; Enums enum State { Off, On } Structs struct Point { int x, y; }

Reference types Classes class Foo: Bar, IFoo {...} Interfaces interface IFoo: IBar {...} Arrays string[] a = new string[10]; Delegates delegate void Empty();

Structure

Like classes, except Stored in-line, not heap allocated Assignment copies data, not reference No inheritance

Ideal for light weight objects Complex, point, rectangle, color int, float, double, etc., are all structs

Benefits No heap allocation, less GC pressure More efficient use of memory

Predefined Types

C# predefined types Reference object, string Signed sbyte, short, int, long Unsigned byte, ushort, uint, ulong Character char Floating-point float, double, decimal Logical bool

Predefined types are simply aliases for system-provided types For example, int == System.Int32

Reserved Keywordsabstract as base Bool break byte casecatch char checked Class const continue decimaldefault delegate do double else enum eventexplicit extern false finally fixed float forforeach goto if implicit in in (generic

modifier)int

interface internal is lock long namespace newnull object operator out out

(genericmodifier)

override params

private protected public readonly ref return sbytesealed short sizeof stackalloc static string structswitch this throw true try typeof uintulong unchecked unsafe ushort using virtual voidvolatileadd alias ascending descending dynamic from getglobal group into join let orderby partial

(type)partial(method)

remove select set

Using System // Namespaceclass Rectangle { // member variables declaration double length; double width; //Method public void Acceptdetails() { length = 10.5; //Assign values to variable width = 6.5; } public double GetArea() { return length * width; } public void Display() { Console.WriteLine("Length: {0}", length); Console.WriteLine("Width: {0}", width); Console.WriteLine("Area: {0}", GetArea()); } }//End class Rectangle class ExecuteRectangle { static void Main(string[] args) { Rectangle objRec = new Rectangle(); //Create Object of Class objRec.Acceptdetails();// Call method objRec.Display(); Console.ReadLine(); } }

Operators

Arithmetic OperatorsRelational OperatorsLogical OperatorsBitwise OperatorsAssignment Operators

Arithmetic operators

Operator Description Example

+ Adds two operands A + B will give 30

- Subtracts second operand from the first A - B will give -10

* Multiplies both operands A * B will give 200

/ Divides numerator by de-numerator B / A will give 2

% Modulus Operator and remainder of after an integer division B % A will give 0

++ Increment operator increases integer value by one A++ will give 11

-- Decrement operator decreases integer value by one A-- will give 9

Relational Operator

Operator Description Example

== Checks if the values of two operands are equal or not, if yes then condition becomes true.

(A == B) is not true.

!= Checks if the values of two operands are equal or not, if values are not equal then condition becomes true.

(A != B) is true.

> Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.

(A > B) is not true.

< Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.

(A < B) is true.

>= Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.

(A >= B) is not true.

<= Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.

(A <= B) is true.

Logical operators

Operator

Description Example

&& Called Logical AND operator. If both the operands are non zero then condition becomes true.

(A && B) is false.

|| Called Logical OR Operator. If any of the two operands is non zero then condition becomes true.

(A || B) is true.

! Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.

!(A && B) is true.

Bitwise OperatorsOperator Description Example

&Binary AND Operator copies a bit to the result if it exists in both operands.

(A & B) will give 12. which is 0000 1100

| Binary OR Operator copies a bit if it exists in either operand. (A | B) will give 61, which is 0011 1101

^Binary XOR Operator copies the bit if it is set in one operand but not both.

(A ^ B) will give 49, which is 0011 0001

~Binary Ones Complement Operator is unary and has the effect of 'flipping' bits.

(~A ) will give -61, which is 1100 0011 in 2's complement due to a signed binary number.

<<

Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand.

A << 2 will give 240, which is 1111 0000

>>

Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand.

A >> 2 will give 15, which is 0000 1111

Assignment Operators

Operator

Description Example

=Simple assignment operator, Assigns values from right side operands to left side operand

C = A + B will assign value of A + B into C

+=Add AND assignment operator, It adds right operand to the left operand and assign the result to left operand

C += A is equivalent to C = C + A

-=Subtract AND assignment operator, It subtracts right operand from the left operand and assign the result to left operand

C -= A is equivalent to C = C - A

*=Multiply AND assignment operator, It multiplies right operand with the left operand and assign the result to left operand

C *= A is equivalent to C = C * A

/=Divide AND assignment operator, It divides left operand with the right operand and assign the result to left operand

C /= A is equivalent to C = C / A

%=Modulus AND assignment operator, It takes modulus using two operands and assign the result to left operand

C %= A is equivalent to C = C % A

<<= Left shift AND assignment operatorC <<= 2 is same as C = C << 2

>>= Right shift AND assignment operatorC >>= 2 is same as C = C >> 2

&= Bitwise AND assignment operatorC &= 2 is same as C = C & 2

^= bitwise exclusive OR and assignment operatorC ^= 2 is same as C = C ^ 2

|= bitwise inclusive OR and assignment operatorC |= 2 is same as C = C | 2

Operator Description Example

sizeof() Returns the size of a data type. sizeof(int), will return 4.

typeof() Returns the type of a class. typeof(StreamReader);

& Returns the address of an variable.

&a; will give actual address of the variable.

Other Operator

Operators Precedence in C#

Category  Operator  Associativity 

Postfix  () [] -> . ++ - -   Left to right 

Unary  + - ! ~ ++ - - (type)* & sizeof  Right to left 

Multiplicative   * / %  Left to right 

Additive   + -  Left to right 

Shift   << >>  Left to right 

Relational   < <= > >=  Left to right 

Equality   == !=  Left to right 

Bitwise AND  &  Left to right 

Bitwise XOR  ^  Left to right 

Bitwise OR  |  Left to right 

Logical AND  &&  Left to right 

Logical OR  ||  Left to right 

Conditional  ?:  Right to left 

Assignment  = += -= *= /= %=>>= <<= &= ^= |=  Right to left 

Comma  ,  Left to right 

Decision Making using C#

Decision making structures require that the programmer specify one or more conditions to be evaluated or tested by the program, along with a statement(s) to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

Statements If {…} If { …} else {…} If {….} else if{…} Nested if statements Switch () case : Ternary operator ( ?: )

If Statement

An if statement consists of a boolean expression followed by one or more statements.

If(boolean_expression) {

/* statement(s) will execute if the boolean expression is true */

}

If …else

• An if statement can be followed by an optional else statement, which executes when the boolean expression is false

if(boolean_expression){ /* statement(s) will execute if the boolean expression is true */}else{ /* statement(s) will execute if the boolean expression is false */}

Nested IF

• You can use one if or else if statement inside another if or else if statement(s).

if( boolean_expression 1){ /* Executes when the boolean expression 1 is true */ if(boolean_expression 2) { /* Executes when the boolean expression 2 is true */ }}

Nested IF Exampleclass Program{ static void Main() {

SampleMethod1(50);SampleMethod2(50);SampleMethod3(50);

}

void SampleMethod1(int value) {

if (value >= 10){ if (value <= 100) {

Console.WriteLine(true); }}

}

void SampleMethod2(int value) {

if (value >= 10 && value <= 100){ Console.WriteLine(true);}

}

void SampleMethod3(int value) {

if (value <= 100 && value >= 10){ Console.WriteLine(true);}

}}

Switch Case

A switch statement allows a variable to be tested for equality against a list of values. Each value is called a case, and the variable being switched on is checked for each switch case.

switch(ch1) { case 'A': printf("This A is part of outer switch" ); switch(ch2) { case 'A': printf("This A is part of inner switch" ); break; case 'B': /* inner B case code */ } break; case 'B': /* outer B case code */}

class SwitchTest{ static void Main() { Console.WriteLine("Coffee sizes: 1=small 2=medium 3=large"); Console.Write("Please enter your selection: "); string str = Console.ReadLine(); int cost = 0;

// Notice the goto statements in cases 2 and 3. The base cost of 25 // cents is added to the additional cost for the medium and large sizes. switch (str) { case "1": case "small": cost += 25; break; case "2": case "medium": cost += 25; goto case "1"; case "3": case "large": cost += 50; goto case "1"; default: Console.WriteLine("Invalid selection. Please select 1, 2, or 3."); break; } if (cost != 0) { Console.WriteLine("Please insert {0} cents.", cost); } Console.WriteLine("Thank you for your business."); }}

Switch Case Example

The ? : Operator

We have covered conditional operator ? : in previous chapter which can be used to replace if...elsestatements. It has the following general form:

Exp1 ? Exp2 : Exp3;Where Exp1, Exp2, and Exp3 are

expressions. Notice the use and placement of the colon.

Loops

A loop statement allows us to execute a statement or group of statements multiple times and following is the general from of a loop statement in most of the programming languages:

For(…) {};While() {}Do{…}While(…);forEach(…)

For Loop

 For loopFor loop is a repetition control structure that

allows you to efficiently write a loop that needs to execute a specific number of times.

for ( init; condition; increment/Decreament ){ statement(s);}

Basic example of for loop

class Program { static void Main(string[] args) { /* for loop execution */ for (int a = 10; a < 20; a = a + 1) { Console.WriteLine("value of a: {0}", a); } Console.ReadLine(); } }

While loop

Repeats a statement or group of statements while a given condition is true. It tests the condition before executing the loop body.

while(condition) { statement(s); }

Example of While

class WhileTest { static void Main() { int n = 2; while (n < 20) { Console.WriteLine("Current value of n is {0}", n); n+=2; } } }

Do While

Like a while statement, except that it tests the condition at the end of the loop body

do{ statement(s);

}while( condition );

Do While Example

public class TestDoWhile { public static void Main () { int x = 2; do { Console.WriteLine(x); x+=2; } while (x < 20); }}

foreach

The foreach statement is used to iterate through the collection to get the information that you want

Does not use integer indexCan be use for Array,Collection , List,Class

Collection Returns each element in orderforeach (CollectionElementType name in Coll

ection) {

 }

ForEach example

class Program   {     static void Main(string[] args)      {        string[] arr = new string[5]; // declaring array         //Storing value in array element        arr[0] = “C#";        arr[1] = “C";        arr[2] = “C++";        arr[3] = “JAVA";        arr[4] = “Android";         //retrieving value using foreach loop        foreach (string name in arr)         {           Console.WriteLine(“Working on" + name);         }        Console.ReadLine();      }   }

Questions ??