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;
        }
    }