Inline switch / case statement in C#

Introduced in C# 8.

You can now do switch operations like this:

FIZZBUZZ switch
{
    "fizz"     => /*do something*/,
    "fuzz"     => /*do something*/,
    "FizzBuzz" => /*do something*/,
    _ => throw new Exception("Oh ooh")
};

Assignment can be done like this:

string FIZZBUZZ = "fizz";
string result = FIZZBUZZ switch
    {
        "fizz"     => "this is fizz",
        "fuzz"     => "this is fuzz",
        "FizzBuzz" => "this is FizzBuzz",
        _ => throw new Exception("Oh ooh")
    };
Console.WriteLine($"{ result }"); // this is fizz

Function calls:

public string Fizzer()     => "this is fizz";
public string Fuzzer()     => "this is fuzz";
public string FizzBuzzer() => "this is FizzBuzz";
...
string FIZZBUZZ = "fizz";

string result = FIZZBUZZ switch
    {
        "fizz"     => Fizzer(),
        "fuzz"     => Fuzzer(),
        "FizzBuzz" => FizzBuzzer(),
        _ => throw new Exception("Oh ooh")
    };
Console.WriteLine($"{ result }"); // this is fizz

Multiple inline-actions per case (delegates are a must I think):

string FIZZBUZZ = "fizz";
string result = String.Empty;

_= (FIZZBUZZ switch
{
    "fizz" => () =>
    {
        Console.WriteLine("fizz");
        result = "fizz";
    },
    "fuzz" => () =>
    {
        Console.WriteLine("fuzz");
        result = "fuzz";
    },
    _ => new Action(() => { })
});

You can read more about the new switch case here: What's new in C# 8.0

In C# 8 you can do something like this

    public Form1()
    {
        InitializeComponent();
        Console.WriteLine(GetSomeString("Fizz"));
    }

    public static string GetSomeString(string FIZZBUZZ) =>
       FIZZBUZZ switch
       {
           "Fizz" => "this is Fizz",
           "Buzz" => "this is Buzz",
           "FizzBuzz" => "this is FizzBuzz",
           _ => "Unknown"
       };

This is equivalent to

    public static string GetSomeString(string FIZZBUZZ)
    {
        switch (FIZZBUZZ)
        {
            case "Fizz": return "this is Fizz";
            case "Buzz": return "this is Buzz";
            case "FizzBuzz": return "this is FizzBuzz";
            default: return "Unknown";
        }
    }

Necromancer poster here

So I took this on as a challenge. Instead of the usual answers of "Just use Switch..Case syntax" statements, I made it a coding challenge of skill and knowledge (not that I have much of either).

Setup

Using .net-4.5.2

public enum FizzBuzz {
    Fizz,
    Buzz,
    FizzBuzz
}

public static class EnumExtension {
    public static void SwitchCase ( this FizzBuzz enm , params KeyValuePair<FizzBuzz , Action> [] parms ) {
        foreach ( var kvp in parms ) {
            if ( kvp.Key == enm ) {
                kvp.Value();
            }
        }
    }
}

Implementation

public class Program {
    static void Main ( string [] args ) {
        var enm = FizzBuzz.Fizz;

        ProcessEnum( enm );
    }

    public static void ProcessEnum ( FizzBuzz enm ) {
        enm.SwitchCase(
            new KeyValuePair<FizzBuzz , Action>( FizzBuzz.Fizz , FizzMethod ) ,
            new KeyValuePair<FizzBuzz , Action>( FizzBuzz.Buzz , BuzzMethod ) ,
            new KeyValuePair<FizzBuzz , Action>( FizzBuzz.FizzBuzz , FizzBuzzMethod )
            );
    }

    private static void FizzMethod () {
        System.Console.WriteLine( "" );
    }
    private static void BuzzMethod () {
        System.Console.WriteLine( "" );
    }
    private static void FizzBuzzMethod () {
        System.Console.WriteLine( "" );
    }

}

A challenge is to use C#8 switch expressions

The problem is that the body of each branch is an expression, not a group of statements.

You can work around this by making each branch return an Action object.

Note the syntax: if I explicitly cast any one of the expressions to the Action type, then the compiler will implicitly cast each of the other expressions. I chose to cast the last (default) expression.

public static void Performction(string input) =>
    (
        (input) switch 
        {   
            "FIZZ" => () => Console.WriteLine("This is the fizz"),
            "BUZZ" => () => Console.WriteLine("This is the buzz"),
            "FIZZBUZZ" => () => 
                {
                    Console.WriteLine("This is a Fizz");
                    Console.WriteLine("But it is a buzz as well!");
                },
            _ => new Action(() => {})
        }
    )();