title: Force refresh image in update panel
body: <p>I have a button and an image in update panel. How do I  force the image refresh by clicking on the button?</p>
  
  <p><strong>update</strong></p>
  
  <p></p>
  
  <pre><code>    &lt;b&gt;Enter the code&lt;/b&gt;
       &lt;asp:UpdatePanel runat="server"&gt;
          &lt;ContentTemplate&gt;
            &lt;uc:TextBox ID="txtCaptcha" runat="server" /&gt;
            &lt;asp:Button ID="btnRefreshCaptcha" runat="server" Text="Refresh the code" CausesValidation="false" onclick="btnRefreshCaptcha_Click" /&gt;
            &lt;/ContentTemplate&gt;
            &lt;Triggers&gt;
              &lt;asp:AsyncPostBackTrigger ControlID="btnRefreshCaptcha" EventName="Click" /&gt;
            &lt;/Triggers&gt;
      &lt;/asp:UpdatePanel&gt;
  </code></pre>