Note: The real advantage of interface is not for supporting multiple inheritance.

Advantage1: We need to declare an interface when we have series of classes which are not having common behavior, still if you want to mandate a method name along with signature and return type and if you want to leave the implementation to the developers of the class.

Advantage2: Interfaces acts as contracts between two developers ( why or how this feature is helpful ?)

Explanation: Assume Developer D1 writing code in class A, this class A requires to call some of the methods present in Class B. Assume class B’s code has to be written by Developer D2. Assume some delay in writing the code happening from  Developer D2. In this situation Developer D1 ccanot be able to complete his code since class A’s code is depending on the Class B’s Code. This kind of dependencied between developers code we can avoid by using interfaces .

Q:How to avoid Dependency?

Ans: Developer 1 D1 has to create an interface I1 with the required method names and signatures along with return types which D1 wanted to use present in Class B, then ask Developer 2 D2 to implement interface I1 in class B.

Public inteface I1

{

int M1(int x,int y);

}

Public class A

{

public int M2(I1 i1)

{

//wrie some code and call inteface i1′s method M1.

i1.M1(10,20);

}

}

Note: In the above sample D2 has to  call the method present in class A by sending his class object as parameter to the method M2.

1. ReferenceEquals and Equals methods behaves same for Reference types but it differs for value types.

2.ReferenceEquals is a Static method and hence we cannot override this method where as Equals method we can override this method.

Ex1:

bool b=0.Equals(0);
bool b1=Object.ReferenceEquals(0, 0);
Response.Write(b);

Ex2:

//Write this code in the main method.

Palle p1 = new Palle(2);
Palle p2 = new Palle(2);
bool b1=p1.Equals(p1);
bool b2=object.ReferenceEquals(p1, p2);
//Both b1 & b2 will be false here

public class Palle
{
public int age;
public Palle(int age)
{
this.age = age;
}
}

Ternary operators can be use full when we have only one simple if else condition.

Ternary Operator Syntax:

condition ? first_expression : second_expression;

Ex:

public class TernaryEx { public int GetBigNum(int a, int b) { return a > b ? a : b; //in the above syntax if a is greater than b //the above expression returns a else it returns b. } }

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is Operator:

• is operator Checks if an object is compatible with a given type
• An is expression evaluates to true if the provided expression is non-null, and the provided object     can  be cast to the provided type without causing  an exception to be thrown.

protected void Page_Load(object sender, EventArgs e)

{

object s1 = “abc”;

object s2 = “abc”;

if (s1 == s2)

{

Response.Write(“value of s1 and s2 are equal”);

}

else if(s1.Equals(s2))

{

Response.Write(“Address of s1 and s2 are equal”);

}

/***************************************************************

* 1.==compares values of the variables.

* 2.Object.Eqals Method compares address of the variables

* **************************************************************/    }

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See the below example to understand the difference between post incrementation and pre incrementation.

int

x = 10;int z;//First assigns value of x (10) to z and then x value incremented to 11.

z=x++;MessageBox.Show(“Post Incement of x=” + z);int y = 20;int a;

//First increments value of y to (21) and assigns 21 to as.a=++y; 

MessageBox.Show(“Pre incrementor Y=”+a);

1.C# is not allowing the multiple inheritance because of the below reason.

Consider the below example:

Order of Catch blocks is very importent while implementing the Catch Blocks.For Example if my code is expected to throw DivideByZeroException , If you know the exception type properly you have to write the specifice expected exception then write generic exception. See below example

Ex: