switch statements and expressions

When if/else gets long

Picking an action based on one value with if/else if gets repetitive:

if (command == "start") Start();
else if (command == "stop") Stop();
else if (command == "pause") Pause();
else Console.WriteLine("Unknown command");

A switch says the same thing more clearly: look at this one value, and pick a branch.

The switch statement

switch (command)
{
    case "start":
        Start();
        break;
    case "stop":
        Stop();
        break;
    case "pause":
    case "hold":            // several cases can share one block
        Pause();
        break;
    default:                // nothing else matched
        Console.WriteLine("Unknown command");
        break;
}

Each section must end with break (or return, throw…). C# doesn't allow one case to "fall through" into the next by accident — a famous source of bugs in C and JavaScript.

Switch expressions: switch that produces a value

Very often you use a switch just to compute a value. Switch expressions do that with much less ceremony:

string emoji = weather switch
{
    "sunny" => "☀️",
    "rainy" => "🌧️",
    "snowy" => "❄️",
    _ => "🤷",          // the discard pattern: anything else
};

• The value comes before switch.
• Each arm is pattern => result, separated by commas.
• _ matches anything — like default.

Patterns make switches powerful

Arms aren't limited to exact values. You can combine values with or, and compare with relational patterns:

string DayType(string day) => day switch
{
    "Saturday" or "Sunday" => "Weekend",
    _ => "Weekday",
};
 
string Grade(int score) => score switch
{
    < 0 or > 100 => "Invalid",
    >= 90 => "A",
    >= 80 => "B",
    >= 70 => "C",
    _ => "F",
};

Arms are tested top to bottom, and the first match wins — so >= 80 is only reached for scores below 90.

Switching on characters, numbers and more

Any type with constant values works:

double Apply(double a, char op, double b) => op switch
{
    '+' => a + b,
    '-' => a - b,
    '*' => a * b,
    '/' => a / b,
    _ => throw new ArgumentException($"Unknown operator {op}"),
};

You'll see much richer patterns — matching on types and object properties — in the Modern C# features module.

Try it

Key takeaways

• switch statements pick a branch based on one value; each section ends with break.
• Switch expressions (value switch { ... }) compute a value concisely.
• _ is the catch-all arm; or combines patterns; <, >= etc. are relational patterns.
• Arms are checked in order — the first match wins.