Indeed, you still need to set page parserpath property.
As you already found, RadCodeBlock
should be used when you have server code blocks placed within the markup. And it is to prevent you from the server error: System.Web.HttpException: The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>).
You should use RadCodeBlock
especially when you have RadAjax on your page.
Unfortunately it could not prevent you from the error you faced.
All the best,
the Telerik team
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