The Old ASP.NET Webforms ReportViewer Malfunctions When ClientIDMode Is Static
|Progress® Telerik® Reporting
|Q2 2012 and later
|Legacy ASP.NET WebForms Viewer
The described scenario and suggested solution relate to the legacy ASP.NET WebForms ReportViewer. It is recommended that you migrate to the HTML5 ReportViewer.
The old ASP.NET Webforms ReportViewer malfunctions when its
ClientIDMode is set to
To solve this issue, refer to the solutions suggested in the ClientIDMode in ASP.NET 4.0 Web Log blog post by Rick Strahl.