New to Telerik UI for ASP.NET AJAX? Download free 30-day trial

Avoid generating multiple controls with the same ID


It is very likely to get the following error message when creating controls at runtime:

Multiple controls with the same ID were found. FindControl requires that controls have unique IDs

In general it indicates that another control with the same ID has been created on a postback of the page.


There are a couple of ways to workaround the above issue:

  • To prevent the postback of the page as implemented in our Load on Demand demo and using the OnClientTabSelecting client side event:
function onTabSelecting(sender, eventArgs) {
  if (args.get_tab().get_pageViewID()) {
  • If you need the page to do a postback you do not need to attach the client-side OnClientTabSelecting event but simply need to check if there is already an existing PageViewId in the OnTabClick server side event handler:!
function RadTabStrip1_tabClick(object sender, RadTabStripEventArgs e) {
  if (e.Tab.PageViewID == null) {
      e.Tab.PageView.Selected = true;
In this article