Question

I am trying for the first time to create an extension method and i am having some trouble… maybe you guys can help out 🙂

public static class Extentions     {         public static int myMethod(this MyClass c)         {               return 1;         }     } 

then when i do ‘MyClass.myMethod’ i get q compiler error saying that the method does not exists…

Why is that?

Answer 1

First, you need a ‘using’ directive to include the namespace that includes your class with extension methods.

Second – re ‘MyClass.myMethod’ – extension methods work on instances, not as static – so you’d need:

MyClass foo = ... int i = foo.myMethod(); // translates as: int i = Extentions.myMethod(foo); 

Finally – if you want to use the extension method inside MyClass (or a subclass), you need an explicit this – i.e.

int i = this.myMethod(); // translates as: int i = Extentions.myMethod(this); 

This is one of the few cases where this matters.