Can I use regex expression in c# with switch case?

Question

Can I write switch case in c# like this?

switch (string)

case [a..z]+

//   do something

case [A..Z]+

//   do something

....

Answer 1

Yes you can in C# 7 (and nobody noticed I had used the incorrect range character in the character class .. instead of -). Updated now with a slightly more useful example that actually works:

using System.Text.RegularExpressions;
string[] strings = {"ABCDEFGabcdefg", "abcdefg", "ABCDEFG"};
Array.ForEach(strings, s => {
    switch (s)
    {
        case var someVal when new Regex(@"^[a-z]+$").IsMatch(someVal):
            Console.WriteLine($"{someVal}: all lower");
            break;
        case var someVal when new Regex(@"^[A-Z]+$").IsMatch(someVal):
            Console.WriteLine($"{someVal}: all upper");
            break;
        default:
            Console.WriteLine($"{s}: not all upper or lower");
            break;
    }
});

Output:

ABCDEFGabcdefg: not all upper or lower
abcdefg: all lower
ABCDEFG: all upper