IIS application pool is not configured for the correct .NET Framework version, or the 32-bit setting is wrong.
In the ecosystem of .NET development, versioning is strict. Many applications built during the late 2000s were compiled specifically against the runtime. If a system lacks version 9.0.0.0, these applications will trigger the "Could not load file or assembly" error, even if a newer version (like v10 or v12) is installed. This makes the 9.0.0.0 download essential for "black box" legacy software that cannot be easily recompiled. Deployment and Availability microsoft.reportviewer.common version 9.0.0.0 download
If your application is throwing an error that it cannot find Microsoft.ReportViewer.Common, Version=9.0.0.0 , follow these steps: IIS application pool is not configured for the correct