If/Else and Switch Expressions

C#'s if/else looks like what you'd expect from a C-family language:

int age = 20;

if (age < 13)
{
    Console.WriteLine("Child");
}
else if (age < 20)
{
    Console.WriteLine("Teenager");
}
else
{
    Console.WriteLine("Adult");
}

One strictness worth flagging: the condition inside if (...) must be a bool. Unlike JavaScript, C# won't let you write if (someNumber) and have it "just work" via truthiness — you'd write if (someNumber != 0) explicitly. This is deliberate; it removes a whole class of "was that supposed to be a comparison?" bugs.

Classic switch statements

string day = "Mon";
switch (day)
{
    case "Mon":
    case "Tue":
    case "Wed":
    case "Thu":
    case "Fri":
        Console.WriteLine("Weekday");
        break;
    case "Sat":
    case "Sun":
        Console.WriteLine("Weekend");
        break;
    default:
        Console.WriteLine("Unknown");
        break;
}

Each case needs a break (or return) — C# doesn't fall through to the next case silently the way C does, and the compiler will actually reject a case with executable code that falls through unintentionally. Stacking cases like case "Mon": case "Tue": with no code in between is fine and common, as shown above.

Switch expressions: the modern, concise form

Since C# 8, switch can also be an expression that produces a value directly, instead of a statement full of breaks:

string category = day switch
{
    "Mon" or "Tue" or "Wed" or "Thu" or "Fri" => "Weekday",
    "Sat" or "Sun" => "Weekend",
    _ => "Unknown",
};

This is shorter, avoids repeated break statements, and reads closer to a lookup table than a sequence of instructions. _ is the discard pattern — it matches anything not already handled, playing the same role default does in a switch statement.

Choosing between them

Reach for a switch expression when you're computing a single value from one input — it's compact and the compiler will warn you if you miss a case on an enum. Reach for if/else or a switch statement when each branch needs to run multiple statements or has side effects beyond producing a value. Both compile down to similar logic; this is purely a readability choice.