In C#, How To Perform Pattern Matching With Switch For Non-Constant String Value?

I'd like to be able to use non-constant string variables as the match target in a switch statement.

I have the code below, but I'm encountering error CS0150: A constant value is expected at case expectedValue:

public bool UseStandardSwitch(string inputValue)
{
    var expectedValue = "SomeValue";

    bool result = default;
    var DoSomething = () => { result = true; };
            
    switch (inputValue)
    {
        case expectedValue:
            DoSomething();
            break;
        default:
            break;
    }
    return result;
}

Is there a way to achieve a similar result?

CodePudding user response：

No need to introduce a variable (as in your answer) - you can use discard with case guard:

public bool UseStandardSwitch(string inputValue)
{
    var expectedValue = Console.ReadLine()!;
    Func<bool> DoSomething = () => true;
    
    return inputValue switch
    {
        _ when inputValue.Equals(expectedValue) => DoSomething(),
        _ when inputValue.Equals(expectedValue   "1") => DoSomething(),
        _ => throw new ArgumentException(),
    };
}

CodePudding user response：

You can use the var pattern to accomplish something similar.

Try this:

public bool UsePatternMatching(string value)
{
    var DoSomething = () => true;

    return value switch
    {
        var str when str.Equals("SomeValue") => DoSomething(),
        _ => throw new ArgumentException(),
    };
}