meet it

A turns a value into an answer.

The switch statement from Level 2 runs blocks of code. A switch expression is shorter and gives back a value: size switch { "S" => 8.5m, "M" => 10m, _ => 13m }. Each line inside is an : a pattern, an arrow, and the answer it gives.

Arms are tried from top to bottom and the first match wins. The underscore _ is a : a pattern that matches anything, so it goes last as a catch-all. Without one, a value that no arm matches crashes with SwitchExpressionException.

using System;

string[] sizes = { "S", "M", "L", "XL" };
foreach (string size in sizes)
{
    Console.WriteLine($"{size}: {Price(size):0.00}");
}

decimal Price(string size) => size switch
{
    "S" => 8.5m,
    "M" => 10m,
    "L" => 11.75m,
    _ => 13m,
};

The comma after the last arm is allowed, and it keeps adding new arms tidy.

guess first

Small letters this time. What will this show?

Guess before you run it. Wrong guesses are how you learn, and nothing is marked.

using System;

Console.WriteLine(Cup("M"));
Console.WriteLine(Cup("m"));

string Cup(string size) => size switch
{
    "S" => "small",
    "M" => "medium",
    "L" => "large",
    _ => "unknown size",
};

your turn

Your turn. Price the delivery options.

Fill in a price for each arm, as decimal values like 3.99m. The last gap is the catch-all arm: write the discard, an arrow and a price.

Your code

output

press run to see what happens

fix it

The greeter crashes on the third country. Can you fix it?

Broken code to fix

output

press run to see what happens

Two lines print, then SwitchExpressionException stops it. Which country has no arm?
No arm matches "JP", and there is no catch-all for anything else.
Add the arm _ => "Hi", as the last line inside the braces, then run.

nailed it

your switches give answers now. :D

A switch expression turns a value into an answer.
Arms are tried from top to bottom, and the first match wins.
End with the discard _ to catch everything else.

new words in your collection

switch expression
arm
discard

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A switch expression turns a value into an answer.

Small letters this time. What will this show?

Your turn. Price the delivery options.

The greeter crashes on the third country. Can you fix it?

your switches give answers now. :D

A turns a value into an answer.