Compiler Error Message: CS0433: The type 'Microsoft.Reporting.WebForms.ReportDataSource' exists in both 'c:\WINDOWS\assembly\GAC_MSIL\Microsoft.Report

One of my friend got this error while working on RDLC Reports in Visual Studio 2008, so here is the solution to this problem that did trick for us to solve this complicated looking error. You just need to go to web.config file and delete these four lines


<add assembly="Microsoft.ReportViewer.WebForms, Version=8.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
<add assembly="Microsoft.ReportViewer.Common, Version=8.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
<add assembly="Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
<add assembly="Microsoft.ReportViewer.Common, Version=9.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>

Happy Coding, Keep Coding.....!