How to enable C# 7 features in existing projects

问题

I am not sure how to use new C# 7 features in existing solution. I tried using pattern matching in a switch statement but I keep getting Value of integral type expected error.

Is there a trick to enable it? I though I can just use new features if I open the solution in VS 2017.

My projects are targeting .net 4.6.2.

Here is the sample code

    private void CS7Test(object o)
    {
        switch (o)
        {
            case null:
                Console.WriteLine("it's a constant pattern");
                break;
            case int i:
                Console.WriteLine("it's an int");
                break;
            case UserInfo p when p.Username.StartsWith("Ka"):
                Console.WriteLine($"a Ka person {p.Username}");
                break;
            case UserInfo p:
                Console.WriteLine($"any other person {p.Username}");
                break;
            case var x:
                Console.WriteLine($"it's a var pattern with the type {x?.GetType().Name} ");
                break;
            default:
                break;
        }
    }

回答1:

Actually it's working without doing any special config. Resharper was giving those errors and after disabling the resharper it worked like a charm.

回答2:

Vs 2017 is configured by default to support c#7.0 with enabling Resharper. You need not to disable it.

In vs 2017 update 3 you can configure it to use the new features of c# 7.1 (and resharper is enabled also).

For more details review: setting c#7.1 in vs2017.3

来源：https://stackoverflow.com/questions/43021529/how-to-enable-c-sharp-7-features-in-existing-projects