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Switch Case

Switch Case

Switch is a selection statement that chooses a switch case section depending on the value matched with the expression/value being evaluated.¹ If none of the case statements match the value of the switched variable, the default path is chosen. The switch statement is like a set of if statements. We exit from the switch by break.

Example

public enum Colors { Red, Blue, Green, Orange }

Colors myColor;

... myColor is set to one of the enum values ...

switch(myColor){
  case Colors.Red: 
    Console.WriteLine("How you like them apples?");
    break;
  case Colors.Blue: 
    Console.WriteLine("Ice Ice Baby...");
    break;
  case Colors.Green: 
    Console.WriteLine("Fore!");
    break;
  default:
    Console.WriteLine("I have a hard time when I try to rhyme.");
}

Output

If myColor is Colors.Red:
> How you like them apples?

If myColor is Colors.Blue:
> Ice Ice Baby...

If myColor is Colors.Green:
> Fore!

If myColor is Colors.Orange:
> I have a hard time when I try to rhyme.

Fallthrough

It is also possible to use multiple statements produce the same outcome, by letting the cases 'fallthrough', like so:

switch(myColor) {
  case Colors.Red:
  case Colors.Blue:
    //Code
    break;
  ...
 }

This will execute the same lines of code if myColor is either Red or Blue.

When clause

Starting with C# 7.0 you can use when clause to specify additional condition that must be satisfied. When clause is optional and is used right after specific case.

Dog dog = new Dog
{
    Name = "Charlie",
    Breed = "Affenpinscher",
    Age = 3
};

switch (dog)
{
    case Dog d when d.Breed == "Affenpinscher" && d.Age >= 6:
        Console.WriteLine($"{dog.Name} is considered a senior dog.");
        break;
    case Dog d when d.Breed == "Affenpinscher" && d.Age >= 2:
        Console.WriteLine($"{dog.Name} is considered an adult dog.");
        break;
    case Dog d when d.Breed == "Affenpinscher":
        Console.WriteLine($"{dog.Name} is considered a puppy.");
        break;
    case Dog d when d.Breed == "Chihuahua" && d.Age >= 4:
        Console.WriteLine($"{dog.Name} is considered a senior dog.");
        break;
    case Dog d when d.Breed == "Chihuahua" && d.Age >= 2:
        Console.WriteLine($"{dog.Name} is considered an adult dog.");
        break;
    case Dog d when d.Breed == "Chihuahua":
        Console.WriteLine($"{dog.Name} is considered a puppy.");
        break;
    default:
        Console.WriteLine($"We have no information according {dog.Breed} breed.");
        break;
}

As you see in the above example after when keyword you should specify logical condition (an instruction that returns bool value).

Sources:

1 https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/switch

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