C# - Switch Keyword in depth

Switch Keyword in C#

1. Basic Example

int number = 3;

switch (number)
{
    case 1:
        Console.WriteLine("Number is 1");
        break;
    case 2:
        Console.WriteLine("Number is 2");
        break;
    case 3:
        Console.WriteLine("Number is 3");
        break;
    default:
        Console.WriteLine("Number not recognized");
        break;
}

Output

Number is 3

2. Switch with Multiple Case Label

In some cases, you may want to execute the same code for multiple values. You can combine multiple values in a single case.'

int dayOfWeek = 2;

switch (dayOfWeek)
{
    case 1:
    case 2:
    case 3:
    case 4:
    case 5:
        Console.WriteLine("Weekday");
        break;
    case 6:
    case 7:
        Console.WriteLine("Weekend");
        break;
    default:
        Console.WriteLine("Invalid day");
        break;
}

Output

Weekday

3. Switch with Patterns (C# 7.0 and Later)

Starting with C# 7.0, you can use pattern matching in switch statements. This allows more flexible matching, such as checking the type of an object or applying more complex conditions.

Type Pattern Matching Example:

object obj = 42;

switch (obj)
{
    case int i:
        Console.WriteLine($"Integer: {i}");
        break;
    case string s:
        Console.WriteLine($"String: {s}");
        break;
    default:
        Console.WriteLine("Unknown type");
        break;
}

Result 

Integer: 42

4. Constant Pattern Matching (C# 9.0 and Later):

You can also match against specific constants with the switch statement.

int month = 3;

switch (month)
{
    case 1:
    case 2:
    case 3:
        Console.WriteLine("Winter");
        break;
    case 4:
    case 5:
    case 6:
        Console.WriteLine("Spring");
        break;
    default:
        Console.WriteLine("Other season");
        break;
}

Result

Winter

5. Switch Expression (C# 8.0 and Later)

In C# 8.0, you can use the switch as an expression, where it returns a value instead of simply executing statements. This is particularly useful for assigning values based on conditions

int number = 2;

var result = number switch
{
    1 => "One",
    2 => "Two",
    3 => "Three",
    _ => "Unknown" // _ is the default case
};

Console.WriteLine(result);

Result 

Two

6.Null Checking in Switch Expression (C# 9.0 and Later)

You can also use switch expressions to check for null values and other patterns more easily.

string input = null;

var result = input switch
{
    null => "Input is null",
    string s when s.Length > 0 => "Non-empty string",
    _ => "Empty string"
};

Console.WriteLine(result);

Result 

Input is null