How to call extension method which has the same name as an existing method? [duplicate]

Question

I have code like

public class TestA {     public string ColA { get; set; }     public string ColB { get; set; }     public string ColC { get; set; }     public void MethodA()     {         MessageBox.Show("Original A1.");     } }  static class ExtenstionTest {        public static void MethodA(this TestA A1)     {         MessageBox.Show("Extended A1.");     } } 

Now if I call MethodA like

TestA a = new TestA();         a.MethodA(); 

It will always call Original method. How can I call the extension method.

Answer 1

You can't call the extension method as a normal extension method. The instance method overrides the extension method with the same signature

EDIT:

You can call it as a static method

ExtensionTest.MethodA(a); 

Answer 2

You can't call it as an extension method. It's basically useless at this point, in terms of being an extension method. (Personally I'd like this to be a warning, but never mind.)

The compiler tries all possible instance methods before it attempts to resolve extension methods. From section 7.6.5.2 of the C# 4 spec:

In a method invocation of one of the forms [...] if the normal processing f the invocation finds no applicable methods, an attempt is made to process the construct as an extension method invociation.

and later:

The preceding rules mean that instance methods take precedence over extension methods

You can call it like a regular static method though:

// Fixed typo in name ExtensionTest.MethodA(a);