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C# Switch Statement

The switch statement in C# allows you to execute different blocks of code based on the value of a variable or expression. It provides a cleaner and more efficient way to compare a single value against multiple possible cases, especially when dealing with numerous conditions.

Key Topics

1. Syntax of Switch Statement

switch (expression)
{
    case value1:
        // Code to execute when expression equals value1
        break;
    case value2:
        // Code to execute when expression equals value2
        break;
    default:
        // Code to execute when none of the cases match
        break;
}

The switch statement evaluates the expression and compares it to each case label. If a match is found, the corresponding code block is executed.

2. Basic Switch Statement Example

Example: Day of the Week

int day = 3;
switch (day)
{
    case 1:
        Console.WriteLine("Monday");
        break;
    case 2:
        Console.WriteLine("Tuesday");
        break;
    case 3:
        Console.WriteLine("Wednesday");
        break;
    case 4:
        Console.WriteLine("Thursday");
        break;
    case 5:
        Console.WriteLine("Friday");
        break;
    case 6:
        Console.WriteLine("Saturday");
        break;
    case 7:
        Console.WriteLine("Sunday");
        break;
    default:
        Console.WriteLine("Invalid day");
        break;
}

Output:

Wednesday

Code Explanation: The variable day is compared against each case. Since day is 3, it matches case 3, and "Wednesday" is printed.

3. Switch with Multiple Case Labels

You can group multiple case labels to execute the same block of code. This is useful when different cases share the same logic.

Example: Weekday or Weekend

int day = 6;
switch (day)
{
    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:

Weekend

Code Explanation: The cases for days 1 to 5 print "Weekday", while cases 6 and 7 print "Weekend". Since day is 6, "Weekend" is printed.

4. Switch with String Cases

The switch statement can also work with strings, allowing you to compare string values.

Example: Fruit Selection

string fruit = "apple";
switch (fruit)
{
    case "apple":
        Console.WriteLine("You chose apple.");
        break;
    case "banana":
        Console.WriteLine("You chose banana.");
        break;
    case "orange":
        Console.WriteLine("You chose orange.");
        break;
    default:
        Console.WriteLine("Unknown fruit.");
        break;
}

Output:

You chose apple.

Code Explanation: The switch compares the string fruit with each case. Since fruit is "apple", it matches the first case, and the message is printed.

5. Switch Expression (C# 8.0+)

In C# 8.0 and later, you can use switch expressions for more concise and expressive code.

Example: Number to Word Conversion

int number = 4;
string result = number switch
{
    1 => "One",
    2 => "Two",
    3 => "Three",
    4 => "Four",
    5 => "Five",
    _ => "Unknown"
};
Console.WriteLine(result);  // Outputs: Four

Output:

Four

Code Explanation: The switch expression matches the value of number to the corresponding string. The underscore (_) represents the default case.

6. Best Practices for Switch Statements

  • Always include a default case to handle unexpected values.
  • Use the switch statement when comparing a single variable against multiple constant values.
  • Ensure that each case ends with a break statement to prevent fall-through.
  • Consider using switch expressions in C# 8.0+ for cleaner code.

Key Takeaways

  • The switch statement simplifies multiple conditional checks against a single value.
  • It enhances code readability and can be more efficient than multiple if-else statements.
  • Switch statements can be used with integral types, strings, and enums.
  • Switch expressions provide a concise syntax for simple value mappings.
  • Proper use of break and default cases is essential for correct control flow.
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