You may receive the following error message When using EO.Web Controls with ASP.NET UpdatePanel:

"An EO.Web control is rendered after an AJAX callback but there wasn't any EO.Web control on the page before the callback. The AJAX rendered EO.Web control will not function correctly under this situation. To correct this problem, please place at least one EO.Web control (an empty EO.Web Callback control, for example) outside of the AJAX update panel so that EO.Web client side script is correctly initialized before the AJAX call."

The key to run any EO.Web control with ASP.NET UpdatePanel is that at least one of our control (any control) must be there before the AJAX call. In another word, we have to "join the party" at the very begining. If we are not there at the very begining and you try to load us midway through an UpdatePanel, you will get that error message.

To avoid this problem you would usually place another EO control outside of the UpdatePanel. The error message suggests an empty Callback control because it does not render anything visually. But any other control will do. We have a free ProgressBar and a free ToolBar control that can be used for that purpose as well. However you would need to place it inside a hidden div so that it's not visible to the end user: