TextBox1.Text = "Button PostBack has been clicked";
When click Button AjaxManager then click Button PostBack, it have an
error occurred below but not often
Webpage error details
Message: Sys.WebForms.PageRequestManagerParserErrorException: The message received from the server could not be parsed. Common causes for this error are when the response is modified by calls to Response.Write(), response filters, HttpModules, or server trace is enabled.
Details: Error parsing near 'Telerik.Web.UI 2010.'.
The specified message is not an error in your code as this is the Telerik trial message. It will stop popping up as soon as you upgrade to the Dev version of the controls.
However please note the it is not suggested to ajaxify particular page content with more than one ajax control. Therefore I suggest that you choose either the RadAjaxManager or the ASP:UpdatePanel in your case but using them both.
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