I have an ASP.NET MVC 5 project in Visual Studio 2017 and after successfully adding C# 7 support (which has worked for me so far), I tried using tuples in my Razor views, but I got a surprising error message:
CS0433: The type 'ValueTuple<T1, T2>' exists in both 'System.ValueTuple, Version=188.8.131.52, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' and 'mscorlib, Version=184.108.40.206, Culture=neutral, PublicKeyToken=b77a5c561934e089'
ValueTuple<int, int> tuple;
Of course I have installed System.ValueTuple as a nuget package
I suspect that's the problem. My guess is that even though you're targeting .NET 4.5.2, you're running on a .NET 4.7 system, and that includes
System.ValueTuple in mscorlib.
I suggest you remove the package dependency on the
System.ValueTuple package, and update your target framework to .NET 4.7 (as you seem to be running on that anyway)... if that change doesn't break other things, of course...