Why does C# allow statements after a case but not before it?

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Because your indentation is misleading, the first code actually is:

var s = "Nice";
switch (s)
{
    case "HI":
        break;
        const string x = "Nice";
    case x:
        Console.Write("Y");
        break;
}

That is, x is declared inside a case statement (though after a break), where it is valid. However, directly inside a switch statement it’s invalid – the only valid statements there are case and default.

Furthermore, const declarations are evaluated at compile time, so x is defined even though there’s a break statement before.

However, note that the Mono C# compiler will not compile this code, it complains that “the name ‘x’ does not exist in the current scope” so Mono seems to implement more checks than the .NET compiler. However, I can’t find any rules in the C# standard which forbid this use of the const declaration so I assume that the .NET compiler is right and the Mono compiler is wrong.

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