ashish

Many times you need to initialize class objects while creating them.One obvious approach is that you can use constructors for this.Suppose if you have declared a class as below:

public class Products
{
public int Category { get; set; }
public int Name { get; set; }

}

As you can see it has no constructor,so if you want to create an object of this class and initialize properties at the same time then you can not do so.
But you can initialize object while creating it using the Object initializer syntax.To initialize an objects properties while creating an object you assign values to the properties in curly braces:

var classObject=new Class{Property1=value1,Property2=value2}

Now you can assign values to the properties of the Products class at initialization as:

var product=new Products{Category=1,Name="Desktop"};

we can also initialize collection objects this way >link to another post

Object initializers for creating Anonymous types

Suppose you want to create a class just for using it single time.You can create anonymous class for this.To create anonymous class you use object initializers.For example,if you want to create an object of anonymous class called product:

var product=new {Category=1,Name="Desktop"};

This is specially useful when you are using LINQ and need to project values not defined in a type.In the following example we are projecting values which are not defined in a type:

var items =
from item in items
select new { item.Name,DateTime.Now };

ashish

Constructor in C#

Constructor is a class method which is called when an object of class is created.Constructor differs from other methods:

• Name of constructor is same as class name
• Constructor method could not return any value

This is the simplest constructor we can declare:

public class ElectronicDevice
{
public ElectronicDevice ()
{
Console.WriteLine ("Creating ElectronicDevice");
}
}

Now when we create an object of the class,the constructor is automatically called:

var obj=new ElectronicDevice();

If we execute that above code then “Creating ElectronicDevice” will be printed

If you want to pass different number and types of values then you can use:

• Constructor Overloading
• Assign Default value to constructor parameter

Constructor Overloading

Assign Default value to constructor parameter

Now if we modify our constructor as below,then we will have to pass an argument when creating an object of the class

public ElectronicDevice(int id)
{
Console.WriteLine("Creating ElectronicDevice");
}

now if we try to create an object of the class without passing an argument then we will get an error.This will throw error:
var obj = new ElectronicDevice();
To prevent this error from occuring we can assign default value to constructor parameter as:

public ElectronicDevice(int id=1)
{
Console.WriteLine("Creating ElectronicDevice");
}

Constructor of Base class

Below we have declared a base class.It defines one parameterless constructor:

public class ElectronicDevice
{
public ElectronicDevice ()
{
Console.WriteLine ("Creating ElectronicDevice");
}
}

This is the derived class.It also defines one parameterless constructor

public class Laptop : ElectronicDevice
{

public Laptop()
{
Console.WriteLine ("Creating Laptop");
}

}

Now when we create an object of derived class,lets see which constructor is called.

using System;

public class Program
{
public static void Main()
{
var obj=new Laptop();
Console.WriteLine("Hello World");
}

}

The constructors are called in the following sequence if you execute the above code.

• ElectronicDevice
• Laptop

Though we have not explicitly called the constructor but it is automatically called when we create an object of the derived class.

If you have defined any parameterized constructors in the base class you need to call them from the derived class using the base keyword

public class Laptop : base(name)
{
}

ashish

Looping means to iterate block of statements over and over based on some condition.C# has several loops based on the requirement.The two main types of loops are the while loop and the for loop.You use the while loop if you want to iterate block of statements based on a boolean condition.On the other hand,you use for loop if you want to loop over statement block based on a condition variable.

Loop variable This is the variable which controls the loop.If the value of this variable is true in the condition block then loop is executed.
If this value is false then the loop exits.We can have multiple loop variables.

There are three important constructs:

1. Initialization block this initializes the loop variable and is executed once at the begining.
2. Condition or Verification block this should return bool value
3. Update block updates the loop variable.this executes after the loop body executes

continue

This statement jumps the execution to next iteration

break

This statement is used to exit from the for loop

Following is the syntax of the for loop:

for(intiailize control variable;boolean condition;update control variable)
{
//statement block
}

The condition is reevaluated after every code block execution and if the condition is false the loop exits.

For example you can use the for loop to iterate from 1 to 15 as:

for(int counter=0;counter<15;counter++)
{
Console.WriteLine("Hello");
}

All of these blocks(1,2 and 3) are optional.So this is a valid for loop.Though this is not useful as it is an infinite loop.

for ( ; ; )
{
//body
}

ashish