CLR20r3 error - Reason and Solution

Recently we were deploying a .NET/SharePoint application in Production environment. Post deployment, when we ran the application, we got error - "Problem Signature CLR20r3"

Reason -

The application was based on .NET 4.5 framework. .NET framework internally uses .NET CLR version 4.0. One of the DLLs we were referencing in our application was built in .NET 3.5 framework. Now .NET 3.5 uses .NET CLR version 2.0.

On the Production server, we only had .NET CLR version 4.0 installed. When our application ran, it looked for both .NET CLR version 4.0 and 2.0 so that it can execute code in all the referenced DLLs. Since .NET CLR version 2.0 was missing, we got this exception.

Solution 1 -

Reference the DLLs built on .NET 4.5 framework version only so that all uses .NET CLR version 4.0

Solution 2 -

If Solution 1 is not feasible, install .NET CLR version 2.0 on the server. This will be installed if you install .NET framework version 2.0 to 3.5.


For more information about .NET framework versions and their relation to .NET CLR versions, refer this blog.