title: asp:RequiredFieldValidator makes postback with empty fields
body: <p>I've faced the following problem with my aps validator. I have a textbox with asp validator. When the user leaves the textbox empty and click on the submit button the validation message shows, but the page does a postback. Any ideas what may cause this happen?</p>
  
  <p>Heres  the validator:</p>
  
  <pre><code>&lt;asp:RequiredFieldValidator ID="valReqName" runat="server" 
      ControlToValidate="txtName" Display="Dynamic" ErrorMessage="blq blq"&gt;
  &lt;/asp:RequiredFieldValidator&gt;
  
  &lt;asp:TextBox ID="txtName" style="font-family:Tahoma, Geneva, sans-serif; 
      color: #4F4F4F;" runat="server"&gt;
  &lt;/asp:TextBox&gt;
  </code></pre>
  
  <p>Many thanks,
  Anton</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>I have two tabs in an UpdatePanel. The validation problem is part of the second tab, where the user makes some inputs. When I've remove this trigger:</p>
  
  <pre><code>&lt;asp:AsyncPostBackTrigger ControlID="lnkUpload" EventName="Click" /&gt;
  </code></pre>
  
  <p>The postback problem was solved, but another problem occurred. Well at least the postback is removed. Thanks for all answers.</p>
  
  <p>(lnkUpload is the id of the second tab linkbutton)</p>
  
  <p><strong>EDIT 2</strong></p>
  
  <p>Well here is the solution. It appears that my problem was the same like in this article. <a href="http://jeffreypaarhuis.com/2011/08/08/validation-not-working-in-updatepanel/" rel="nofollow">http://jeffreypaarhuis.com/2011/08/08/validation-not-working-in-updatepanel/</a></p>