title: Implement extension method interface C#
body: <p>I am newbie to C#, and have a problem with understanding how should I implement an extension method of interface. I didn't found any material about this issue. From the material I found about general extension methods in C# I expected the following simple demonstrating example work:</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  namespace testExtension
  {
  public  interface  IcheckThingsOut
  {
     bool x();
  }
  public static class extensionInterface
  {
     public static bool y(this IcheckThingsOut bla) { return true;}
  }
  public class implementInteface : IcheckThingsOut
  {
     bool IcheckThingsOut.x()
     {
         return true;
     }
     bool IcheckThingsOut.y()
     {
         return false;
  
     }
  }
  }
  </code></pre>
  
  <p>But the compiler is still not satisfied. What did I miss, and what is the right syntax here (with the same semantics as the code)?</p>