title: downgrade .net 4.5 application to 4.0
body: <p>I want to downgrade a .net library from framework version 4.5 to .net 4.0.</p>
  
  <p><strong>I have several libs installed using nuget:</strong></p>
  
  <ul>
  <li>Microsoft.AspNet.WebApi.Client and it's dependencies:</li>
  <li>Newtonsoft.Json </li>
  <li>System.Net.Http (Microsoft .Net 4 HTTP Client Libraries)</li>
  </ul>
  
  <p><strong>I do the following</strong>:</p>
  
  <ul>
  <li><p><em>In settings of each project in my solution I set target framework to 4.0</em> . After it I tried to rebuild my solution but of course without success because of error <code>The type or namespace name 'Newtonsoft' could not be found (are you missing a using directive or an assembly reference?)</code>, the same for HTTP Client libs</p></li>
  <li><p><em>Using nuget ui manager I removed dependencies and tried to reinstall</em>. But there is an error <code>Could not install package 'Microsoft.AspNet.WebApi.Client 5.1.1'. You are trying to install this package into a project that targets '.NETFramework,Version=v4.0', but the
  package does not contain any assembly references or content files that are compatible with that framework. For more information, contact the package author.</code></p></li>
  </ul>
  
  <p>My question is: can I downgrade this project or I should replace these libs with some that support .net 4 and rewrite some parts of code?</p>