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

This doesn't make sense. We've had a line of code like this in our application since 2009

String.Format(CultureInfo.CurrentCulture, "You must specify a new password of {0} or more characters.", _membershipService.MinPasswordLength);

Recently we upped the project to .NET 4.6 and now, for me at least, this line breaks with the same error. So obviously the new overload is breaking something, and the method is not new.