Compiler Error CS1020

Overloadable binary operator expected

An attempt was made to define an operator overload, but the operator was not an overloadable binary operator, which takes two parameters. For the list of overloadable operators, see the Overloadable operators section of the Operator overloading article.

The following sample generates CS1020:

// CS1020.cs  
public class iii  
{  
   public static int operator ++(iii aa, int bb)   // CS1020, change ++ to +  
   {  
      return 0;  
   }  
  
   public static void Main()  
   {  
   }  
}