Question

Is there a situation in which we need to have an extension method with a default value of an object being extended?

For example,

public static class util
{
  public static string Foo(this string name="Hello world")
  {
     return name;
  }
}

Answer 1

I am not sure if any such situation will arise, but you can’t do that. You will get an error:

Cannot specify a default value for the ‘this’ parameter