title: TextboxChanged Event not firing in Update Panel
body: <p>I want to fire the TextChanged event of a TextBox inside an UpdatePanel so I can do something with the input of the user. </p>
  
  <p>What I have come up with so far is the following code:</p>
  
  <pre><code>&lt;asp:GridView ID="gdBestellliste" AutoGenerateColumns="false" runat="server"
                      Width="100%" AllowPaging="false" GridLines="Horizontal" EnableModelValidation="true"
                      BorderColor="#6893CF" PagerStyle-BackColor="#F0F0F0" HeaderStyle-Height="20" ShowFooter="false"&gt;
       &lt;Columns&gt;
  
            &lt;asp:TemplateField HeaderText="Amount to order" HeaderStyle-BorderStyle="None" HeaderStyle-HorizontalAlign="left" HeaderStyle-Width="70px"
                               ItemStyle-HorizontalAlign="left" ItemStyle-Wrap="false" ItemStyle-VerticalAlign="Middle" ItemStyle-CssClass="DataCell"&gt;
  
                 &lt;ItemTemplate&gt;
                      &lt;asp:UpdatePanel runat="server"&gt;
                           &lt;ContentTemplate&gt;
                                &lt;asp:TextBox runat="server" ID="tbProductLookup" OnTextChanged="tbProductLookup_Changed" AutoPostBack="true"&gt;&lt;/asp:TextBox&gt;
                           &lt;/ContentTemplate&gt;
                      &lt;/asp:UpdatePanel&gt;
                 &lt;/ItemTemplate&gt;
  
            &lt;/asp:TemplateField&gt;
  
       &lt;/Columns&gt;
  
  &lt;/asp:GridView&gt;
  </code></pre>
  
  <p>My problem here is that when I make an input in the Textbox and afterwards the TextChanged event trys to fire I get an error from the Internet Explorer debugger: </p>
  
  <pre><code>Sys.WebForms.PageRequestManagerServerErrorException: GUID should contain 32 digits with 4 dashes
  </code></pre>
  
  <p>It never gets to the codebehind method that I defined for the TextChanged event.</p>
  
  <p>So what am I doing wrong? Any help will be appreciated :)</p>
  
  <p><strong>Update:</strong>
  Seems like a part of my problem was misinformation from my part. I assumed that only the needed part of the code behind will be loaded by the update panel which I now learned is utterly wrong. And therefore somewhere in my code behind an empty GUID was created which ultimately led to the PageRequestManagerServerErrorException.</p>
  
  <p>Good, finally I have got no error message anymore but I still can't use the TextChanged event. </p>
  
  <p>I don't know if this is of any help but I discovered that when I first write something in my TextBox and leave it nothing happens. But when I write something into the TextBox and leave it again a postback (no asynchronous) occurs.</p>
  
  <p>What the hell is going on?  </p>