The Microsoft.ReportViewer.Common dynamic-link library (DLL) is a critical core component of Microsoft's Reporting Services. Version 9.0.0.0 corresponds directly to the Visual Studio 2008 ecosystem and the .NET Framework 3.5 runtime. If you are maintaining legacy enterprise software, running older .NET applications, or migrating systems, you will likely encounter errors pointing to this specific missing assembly.
The safest way to get version 9.0.0.0 is by installing the full runtime package, which automatically registers the correct DLLs into the GAC. Visit the official Microsoft Download Center. microsoft.reportviewer.common version 9.0.0.0 download
If your application uses a mix of versions, you can use binding redirects in your configuration file to force all references to a specific version. The Microsoft
"Could not load file or assembly 'Microsoft.ReportViewer.Common, Version=9.0.0.0'" running older .NET applications