c# - Extension method on type -

Is there a way to create an extension method for that type? I am able to make them for examples.

  public static class MyExtensions {public static string test (this string) {return "test"; }} Public class test {static zero test it} {string.Test ()); // string will not compile the s = null; S.Test (); }}  

No, this is not possible. Extension methods can only be made for example