Method not found: 'System.String System.String.Format(System.IFormatProvider, System.String, System.Object)

Question

I have a Web API 2 project with help pages that runs fine locally but throws this error when I push it to Azure:

Method not found: \'System.String Sys

Answer 1

In case this helps anyone. We encountered this issue recently after upgrading our development environment to VS2015 (Our target environment is .Net 4)

Our C++/clr projects had not been setup correctly to use the /clr switch i.e. they were set to no common language support, even though we were using the clr. This didn’t cause an issue until we upgraded to VS2015.

I’m not completely clear on why this works. I’m guessing c++/clr project must bind to a specific version of the CLR runtime at compile time. I’d be interested if someone could explain this more clearly.