: The most reliable way to get this specific assembly is by installing the Microsoft Report Viewer 2008 SP1 Redistributable . This package installs the necessary DLLs to the Global Assembly Cache (GAC).
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.
: Historically, this was available through the Microsoft Download Center . If the direct landing page for the "2008 Redistributable" is retired, it is often bundled with the SQL Server 2008 R2 Reporting Services or Visual Studio 2008 installation media.
Here are some key points about the Microsoft.ReportViewer.Common version 9.0.0.0:
Add the following to your app.config or web.config :