using System;
class csrefKeywordsOperators
   {
       class Base
       {
           public override string  ToString()
           {
	             return "Base";
           }
       }
       class Derived : Base 
       { }
 
       class Program
       {
           static void Main()
           {
 
               Derived d = new Derived();
 
               Base b = d as Base;
               if (b != null)
               {
                   Console.WriteLine(b.ToString());
               }
 
           }
       }
   }

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