Compiler Error CS0556

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User-defined conversion must convert to or from the enclosing type

A user-defined conversion routine must convert to or from the class that contains the routine.

The following sample generates CS0556:

// CS0556.cs
namespace x
{
   public class ii
   {
      public class iii
      {
         public static implicit operator int(byte aa)   // CS0556
         // try the following line instead
         // public static implicit operator int(iii aa)
         {
            return 0;
         }
      }

      public static void Main()
      {
      }
   }
}