Why not allow Extension method definition in nested class?
===

I would find it convenient/logical to write my exensions for a class in a nested class.  The main reason is I could simply name that class `Extensions` and let it's outer naming scope define it.

What is the technical reason to disallow something like:

    public class Foo
    {
       ObjectSet<Bar> Bars { get; set; }
    
       public static class Extensions
       {
          public static Bar ByName(this ObjectSet<Bar> bars, string name)
          {
             return bars.FirstOrDefault(c => c.Name == name);
          }
       }
    }

Whereas now I have to create a separate free standing class.

