The ReportViewer control not working quiet right? It may not be your code but the version of Microsoft.ReportViewer.WebForms.dll you have installed.
I believed I was working with the latest version of Microsoft.ReportViewer.WebForms. I check the C:\WINDOWS\assembly folder and it said Microsoft.ReportViewer.WebForms version 8.0.0.0, all good and well I believed.
I was wrong I did a quick search of my machine and I found 3 version of the Microsoft.ReportViewer.WebForms that all report to be Assembly Version 8.0.0.0. It is not until you check the file version or product version of each of the DLL that you notice a difference. All my issue was because I was using File Version 8.0.50727.762
I’ve now installed File Version 8.0.50727.817 and my initial testing seems to show that my issue has been fixed.
Microsoft.ReportViewer.WebForms.dll File Version 8.0.50727.817
Microsoft.ReportViewer.WebForms.dll File Version 8.0.50727.762
Microsoft.ReportViewer.WebForms.dll File Version 8.0.50727.42