Control Flow

Switch Statements

A switch statement chooses a case based on a value.

switch case A switch case handles one matching value inside a switch statement.

Switch Statements

day
SwitchStatement.cs
Replay: real traced execution (multi-file project)
using System;

class Program
{
    static void Main()
    {
        int day = 2;
        string label;

        switch (day)
        {
            case 1:
            case 2:
            case 3:
            case 4:
            case 5:
                label = "weekday";
                break;
            case 6:
            case 7:
                label = "weekend";
                break;
            default:
                label = "invalid";
                break;
        }

        Console.WriteLine($"day={day}");
        Console.WriteLine($"label={label}");
    }
}

using System;

class Program
{
    static void Main()
    {
        int day = 6;
        string label;

        switch (day)
        {
            case 1:
            case 2:
            case 3:
            case 4:
            case 5:
                label = "weekday";
                break;
            case 6:
            case 7:
                label = "weekend";
                break;
            default:
                label = "invalid";
                break;
        }

        Console.WriteLine($"day={day}");
        Console.WriteLine($"label={label}");
    }
}

using System;

class Program
{
    static void Main()
    {
        int day = 9;
        string label;

        switch (day)
        {
            case 1:
            case 2:
            case 3:
            case 4:
            case 5:
                label = "weekday";
                break;
            case 6:
            case 7:
                label = "weekend";
                break;
            default:
                label = "invalid";
                break;
        }

        Console.WriteLine($"day={day}");
        Console.WriteLine($"label={label}");
    }
}

  1. day ← 2

    4{5    static void Main()6    {7        int day→ 2 = 2; //@day=6, 98        string label;

  2. switch (day)

    10switch (day2)11{12    case 1:13    case 2:

  3. label ← weekday

    11{12    case 1:13    case 2:14    case 3:15    case 4:16    case 5:17        label→ weekday = "weekday";18        break;19    case 6:

  4. Console.WriteLine($"day={day}");

    28    Console.WriteLine($"day={day2}");29    Console.WriteLine($"label={labelweekday}");30}
    outputday=2
label=weekday

  1. day ← 6

    4{5    static void Main()6    {7        int day→ 6 = 6;8        string label;

  2. switch (day)

    10switch (day6)11{12    case 1:13    case 2:

  3. label ← weekend

    18    break;19case 6:20case 7:21    label→ weekend = "weekend";22    break;23default:

  4. Console.WriteLine($"day={day}");

    28    Console.WriteLine($"day={day6}");29    Console.WriteLine($"label={labelweekend}");30}
    outputday=6
label=weekend

  1. day ← 9

    4{5    static void Main()6    {7        int day→ 9 = 9;8        string label;

  2. switch (day)

    10switch (day9)11{12    case 1:13    case 2:

  3. label ← invalid

    22        break;23    default:24        label→ invalid = "invalid";25        break;26}

  4. Console.WriteLine($"day={day}");

    28    Console.WriteLine($"day={day9}");29    Console.WriteLine($"label={labelinvalid}");30}
    outputday=9
label=invalid

Match the Day

  1. day starts at 2.
  2. The switch checks the grouped cases.
  3. case 2 is in the weekday group.
  4. label becomes weekday. | Day | Case group | Label | | --- | --- | --- | | 2 | 1 through 5 | weekday | | 6 | 6 or 7 | weekend | | 9 | default | invalid |

Exercise: SwitchStatement.cs

Use switch cases to label a day as weekday, weekend, or invalid