title: The control with ID 'UpdatePanel1' requires a ScriptManager on the page
body: <p>I'm using ASP.NET and testing a update panel. I know it does require a scriptmanager and I looked at all other similar questions in SO but no one answers my case.</p>
  
  <p>Here is my code:</p>
  
  
  
  <pre><code>&lt;!DOCTYPE html&gt;
  
  &lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;
  &lt;head runat="server"&gt;
      &lt;title&gt;&lt;/title&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;form id="form1" runat="server"&gt;
      &lt;div&gt;
  
          This is Form A&lt;/div&gt;
          &lt;asp:ScriptManager ID="aa" runat="server"&gt;&lt;/asp:ScriptManager&gt;
          &lt;asp:UpdatePanel ID="UpdatePanel1" runat="server"&gt;
              &lt;ContentTemplate&gt;
                  &lt;asp:TextBox ID="TextBox1" runat="server"&gt;&lt;/asp:TextBox&gt;
                  &lt;asp:Button  Text="OK" runat="server"/&gt;
              &lt;/ContentTemplate&gt;
          &lt;/asp:UpdatePanel&gt;
      &lt;/form&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>So As you see I do have a scriptmanager and still getting this error. </p>
  
  <p>Feedbacks Appreciated.</p>
  
  <p>==============================</p>
  
  <p>None of similar questions is SO answers my question as "I Already do have a ScriptManager" in my code.</p>