C# Error CS1105 – Extension method must be static

C# Error

CS1105 – Extension method must be static

Reason for the Error & Solution

Extension methods must be static.

Extension methods must be declared as static methods in a non-generic static class.

Example

The following example generates CS1105 because Test is not static:

// cs1105.cs  
// Compile with: /target:library  
public class Extensions  
{  
  
    // Single type parameter.  
        public void Test<T>(this System.String s) {} //CS1105  
  
}