Adding PostBackTrigger and AsyncPostBackTriggers to UpdatePanel for dynamically generated checkboxes with checkedChanged EventHandler

Question

For more clear explanation here's my code on .asp file:

<asp:UpdatePanel ID="updPnlTabs" runat="server" >
   <Triggers>
    <asp:PostBackTrigger ControlID="btnSave" />
   </Triggers>
  <ContentTemplate>
   <asp:Panel ID="pnlCheckList" runat="server" style="margin-bottom: 10px;" CssClass="listingDummyTab">
   </asp:Panel>
  </ContentTemplate>
</asp:UpdatePanel>

On my .cs code, I dynamically created checkeboxes to the pnlCheckList like this:

CheckBox chkModuleID = new CheckBox();
chkModuleID.ID = drNew[def.ID].ToString();
chkModuleID.AutoPostBack = true;
chkModuleID.CheckedChanged += new EventHandler(chkID_OnRow_Check);
pnlCheckList.Controls.Add(chkModuleID);

Now my problem here is when I change the check boxes the whole page have to load instead of the content of the UpdatePanel . Note that the EventHandler for the dynamically created checkboxes is firing but not inside the UpdatePanel.

How can I add the ID 's of the dynamically created Controls in <Triggers> of the UpdatePanel ?

Answer 1

There is no way of adding dynamic (or programmatically created) controls to the markup, therefore, you must register the control with the ScriptManager after creating it.

Per the AsyncPostBackTrigger documentation , adding an AsyncPostBackTrigger control programmatically is not supported:

To programmatically register a postback control, use the RegisterAsyncPostBackControl method of the ScriptManager control. Then call the Update method of the UpdatePanel control when the control posts back.

---

Basically what you should be doing is registering the CheckBox control after creating it.

// original code
CheckBox chkModuleID = new CheckBox();
chkModuleID.ID = drNew[def.ID].ToString();
chkModuleID.AutoPostBack = true;
chkModuleID.CheckedChanged += new EventHandler(chkID_OnRow_Check);
pnlCheckList.Controls.Add(chkModuleID);

// register the control to cause asynchronous postbacks
ScriptManager.GetCurrent(this).RegisterAsyncPostBackControl(chkModuleID);

Important: Inside of your chkID_OnRow_Check callback/eventhandler function, ensure you call UpdatePanel1.Update() .

Update 2013-02-20

Due to the my understanding of the exception you are receiving, consider making the CheckBox IDs unique.

// One possibility is this - assuming you don't require a consistent ID
chkModuleID.ID = String.Format("{0}-{1}", drNew[def.ID].ToString(), Guid.NewGuid().ToString("N"));