Hello Friends, In this blog I will explain what is Extension method in c# ?

Extension Methods:- Extension method helps you to add new methods to an existing types (like any Predefined dll or class etc.) without creating new derived types or modifying the original types.

Example:- In development you are using many third party components. In below code I have used one third party dll for performing the mathematical operation like addition, subtraction and multiplication etc.

 class MathematicalOperation
{
  static void Main (string [] args)
  {
     MathsOperation objectMathsOperation  =new MathsOperation()  // third party dll initialization 
     Console.WriteLine(objectMathsOperation.Addition(45,40));  //calling dll addition methods and taking input
     Console.ReadLine(); //Read the input
  }
} 

In above example we are using third party Addition methods using two input parameter. But Now we need to perform five numbers addition, subtraction etc. So we can achieve this functionality in many ways like create your own custom function, or may be added a new methods on third party dll. But in most of cases we have not third dll source code. So we can create extension methods for achieving this.

Extension method creation :-

public static class AddExtensionMethods
{
  public static int FiveElementsAdditions(this MathsOperation  obj,int i, intj,int k, int l, int m)
  {
// this MathsOperation  obj  is used to define the extension methods.
    return int i+ int j +int k +int l +int m ;
   }
}

After creating above function we can easily use FiveElementsAdditions methods.

 class MathematicalOperation
{
  static void Main (string [] args)
  {
     MathsOperation objectMathsOperation  =new MathsOperation()  // third party dll initialization 
     Console.WriteLine(objectMathsOperation.FiveElementsAdditions (45,40,10,12,8));  //calling extension methods and taking input
     Console.ReadLine(); //Read the input
  }
}