Even if you have SQL Server 2016 or 2019 installed, the 9.0.0.0 DLL will not be present unless you explicitly install the correct redistributable package.
A: Go to Control Panel > Programs and Features. Look for "Microsoft Report Viewer 2010 Redistributable". Uninstall it, then manually remove any local DLL copies from your project. microsoft.reportviewer.common version 9.0.0.0 download
As Version 9.0.0.0 is quite old (circa 2008), be aware of potential security vulnerabilities. Microsoft has released newer versions (Report Viewer 2010, 2012, 2015, 2019). If possible, you should update your application to use the newer runtimes to ensure compatibility with modern Windows Server environments and security patches. Even if you have SQL Server 2016 or 2019 installed, the 9
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 Uninstall it, then manually remove any local DLL