This is a generic error and usually means that there is a mismatch in your referenced assemblies and the actual ones used. Most likely you have side-by-side reporting installations and have mismatched references. Please use the Upgrade Wizard to upgrade your projects containing Telerik reports and rebuild them. If you have added manual references i.e. Copy Local = True, then delete all assemblies from the \bin folder, re-add proper references in the project and rebuild the project after that. If the problem still occurs make sure that you have specified the full assembly qualified name in each reference. For example:
<%@ Register assembly="Telerik.ReportViewer.WebForms, Version=184.108.40.2068, Culture=neutral, PublicKeyToken=a9d7983dfcc261be
" namespace="Telerik.ReportViewer.WebForms" tagprefix="telerik" %>
as opposed to:
<%@ Register TagPrefix="telerik" Assembly="Telerik.ReportViewer.WebForms" Namespace="Telerik.ReportViewer.WebForms" %>
Hope this helps.
the Telerik team
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