title: The type or namespace name 'ToolkitScriptManager' does not exist in the namespace 'AjaxControlToolkit' in ASP.NET Webforms
body: <p>I'm using ASP.NET Webforms and adding AjaxControlToolkit in my master page and I'm getting this error:
  The type or namespace name 'ToolkitScriptManager' does not exist in the namespace 'AjaxControlToolkit' (are you missing an assembly reference?) </p>
  
  <p>This is my code:</p>
  
  <p>Page.Master.designer.cs:</p>
  
  <pre><code> protected global::AjaxControlToolkit.ToolkitScriptManager ToolkitScriptManager1;
  </code></pre>
  
  <p>Page.Master(aspx page):</p>
  
  <pre><code>&lt;%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %&gt;
  
  &lt;asp:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server"&gt;
      &lt;/asp:ToolkitScriptManager&gt;
  </code></pre>
  
  <p>web.config:</p>
  
  <pre><code>&lt;add tagPrefix="asp" namespace="AjaxControlToolkit" assembly="AjaxControlToolkit" /&gt;
  </code></pre>
  
  <p>I've added AjaxControlToolkit.dll as a reference in my project as well. I've tried almost all the answers for similar questions but nothing worked. What am I doing wrong?</p>