title: AjaxControlToolkit configuration in web.config update from 3.5 to 4.1.51116.0
body: <p>I added the AjaxControlToolkit with the NuGet Manager Console.</p>
  
  <p>Now I get the this error:</p>
  
  <p><strong>Assembly 'AjaxControlToolkit, Version=4.1.51116.0, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e' uses 'System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' which has a higher version than referenced assembly 'System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'</strong></p>
  
  <p>But if I change the Version to 4.0.0.0 as it is in my other project that works, it wont work and still gives me the same error.</p>
  
  <p>this is the Toolkit part in my web.conifg:</p>
  
  <pre><code>&lt;controls&gt;
              &lt;add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
              &lt;add tagPrefix="asp" namespace="System.Web.UI.WebControls" assembly="System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
              &lt;add tagPrefix="ajaxToolkit" assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" /&gt;
  &lt;/controls&gt;
  </code></pre>
  
  <p>Would be nice if someone could explain it to me, what im doing wrong? :)</p>
  
  <p>p.s I am new in .Net</p>