title: Why can't I reference System.Runtime.Serialization.Json in C#
body: <p>I want to use an API to get info from the interwebz. The API returns data in Json format.</p>
  
  <ol>
  <li>I'm running Microsoft Visual Studio C# 2010 Express addition.</li>
  <li>It appears that I have the .NET Framework 4 Client Profile set as my
  "Target framework" but I'm honestly not sure exactly what this
  means.</li>
  <li>This is a Windows Forms Application...</li>
  </ol>
  
  <p>Not much code to show because I can't really get started without the appropriate using statement...</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Windows.Forms;
  using System.Net;
  using System.Runtime.Serialization.Json;
  </code></pre>
  
  <p>I get this error:</p>
  
  <blockquote>
    <p>The type or namespace name 'Json' does not exist in the namespace
    'System.Runtime.Serialization' (are you missing an assembly
    reference?)</p>
  </blockquote>
  
  <p>Am I missing a DLL file or something? Based on my hours of fruitlessly searching for solutions, I understand that the .NET 4.xx should already have the tools needed to parse up a Json formatted string?</p>