title: F# type extensions in C# project: System.Runtime.CompilerServices.Extension missed?
body: <p>I'm diving into F# and it's very fascinating. I'm trying to marry Optional Types and C# like <a href="https://stackoverflow.com/questions/702256/f-extensions-in-c/702321#702321">here</a>. Pretty interesting thing... however I miss something important I guess:</p>
  <pre><code>#light
  namespace MyFSharp
  
  // C# way
  [&lt;System.Runtime.CompilerServices.Extension&gt;]
  module ExtensionMethods =
      [&lt;System.Runtime.CompilerServices.Extension&gt;]
      let Great(s : System.String) = &quot;Great&quot;
  
  
  using System;
  using MyFSharp;  // reference the F# dll
  class Program
  {
      static void Main(string[] args)
      {
          var s = &quot;foo&quot;;
          //s.Awesome(); // no
          Console.WriteLine(s.Great());  // yes
      }
  }
  </code></pre>
  <p>That's very simple - and I guess it's too early for me or something... I get:</p>
  <pre><code>The type 'Extension' is not defined 
  </code></pre>
  <p>Maybe it's too early... but I just don't get why it isn't found.</p>
  <p>Thanks,
  Marius</p>