Please check the following help article: http://www.telerik.com/help/aspnet-ajax/xmlhttppanel-vs-radajaxpanel.html
. RadXmlHttpPanel uses client callbacks and web services, which do not offer a ViewState and only a few of the page lifecycle events are raised.
Most probably the values of the RadTextBox
controls are lost because of the limitations mentioned above. I would suggest replacing the RadXmlHttpPanel with a RadAjaxPanel or an UpdatePanel and if the values of the text boxes are persisted to keep this change as in this case it would appear that performing a partial postback is more suitable.
DevCraft Q1'14 is here! Watch the online conference to see how this release solves your top-5 .NET challenges. Watch on demand now.