Switch-Case Statement in C#

In C#, the switch-case statement is a control flow structure that allows you to execute different blocks of code based on the value of a variable. It provides an alternative to using multiple if-else statements and can make your code more readable and efficient when dealing with multiple conditions.

Syntax of `switch-case`

Here’s the basic syntax of a switch-case statement in C#:

csharp

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

Expression: The value being checked (e.g., an integer, string, or enum).
Case values: Values that are compared with the expression.
Break: Prevents fall-through to the next case.
Default: An optional block that executes if no case matches.

Example 1: Simple `switch-case` Statement

csharp

int day = 3;

switch (day)
{
    case 1:
        Console.WriteLine("Monday");
        break;
    case 2:
        Console.WriteLine("Tuesday");
        break;
    case 3:
        Console.WriteLine("Wednesday");
        break;
    default:
        Console.WriteLine("Invalid day");
        break;
}

Breakdown:

The switch-case checks the value of day.
Since day equals 3, "Wednesday" is printed.
The default case is executed if the value of day doesn't match any case.

Real-Life Example

Consider a vending machine that sells different drinks:

If the customer selects 1, they get a soda.
If they select 2, they get water.
If they select 3, they get juice.

Here’s how this logic looks in C#:

csharp

int selection = 2;

switch (selection)
{
    case 1:
        Console.WriteLine("Dispensing Soda");
        break;
    case 2:
        Console.WriteLine("Dispensing Water");
        break;
    case 3:
        Console.WriteLine("Dispensing Juice");
        break;
    default:
        Console.WriteLine("Invalid selection");
        break;
}

In this case, if the user selects 2, "Dispensing Water" is printed.

Best Practices for `switch-case` Statements

Use switch-case for Multiple Conditions: If you’re checking the same variable against multiple values, switch-case is more efficient and readable than if-else.
Example:

csharp

switch (value)
{
    case 1: 
    case 2: 
    case 3:
        // Handle these cases similarly
        break;
}

Always Include a default Case: The default block acts as a safety net if none of the cases match. It's important to handle unexpected inputs.
Avoid Fall-Through: In C#, you must explicitly break out of each case to avoid unintended fall-through to the next case. This is different from languages like C, where fall-through is allowed.
Keep switch Statements Simple: Avoid overly complex switch statements with too many cases. If you find yourself with more than 5–7 cases, consider using other structures like enums or polymorphism.
Use switch-case with Enums for Better Code Readability: When possible, use enums with switch-case to make your code more meaningful.
Example:

csharp

enum Color { Red, Green, Blue }

switch (color)
{
    case Color.Red:
        // Code for red
        break;
    case Color.Green:
        // Code for green
        break;
}

Features of `switch-case` Statements

Efficient Execution: For large sets of conditions, switch-case can be faster than if-else, especially when there are many comparisons.
Cleaner Syntax: switch-case provides a clear, structured way to handle multiple conditions, improving code readability.
Supports Multiple Data Types: The switch-case statement works with various data types, including integers, strings, and enums.
Use of goto case and goto default: Allows jumping between cases, though it's generally considered poor practice as it can lead to complex, hard-to-read code.
Pattern Matching Support (C# 7.0+): Modern versions of C# allow pattern matching within switch-case, adding more flexibility and power to the structure.

`switch-case` vs `if-else`

Both switch-case and if-else statements are used to make decisions in code, but switch-case is often preferred when:

You are checking the value of a single variable against many possible options.
The code becomes too cluttered with nested if-else statements.
You want a cleaner, more readable alternative.

For example:

csharp

int score = 90;

if (score >= 90)
{
    Console.WriteLine("Grade A");
}
else if (score >= 80)
{
    Console.WriteLine("Grade B");
}
else if (score >= 70)
{
    Console.WriteLine("Grade C");
}
else
{
    Console.WriteLine("Grade D");
}

This logic can be simplified with switch-case:

csharp

int score = 90;

switch (score / 10)
{
    case 9:
    case 10:
        Console.WriteLine("Grade A");
        break;
    case 8:
        Console.WriteLine("Grade B");
        break;
    case 7:
        Console.WriteLine("Grade C");
        break;
    default:
        Console.WriteLine("Grade D");
        break;
}

Real-Life Scenario for `switch-case`

Let’s say you are working on a pizza ordering system where customers can choose different sizes of pizza, and the price is determined based on the selected size:

csharp

string pizzaSize = "Large";

switch (pizzaSize)
{
    case "Small":
        Console.WriteLine("The price is $5.");
        break;
    case "Medium":
        Console.WriteLine("The price is $7.");
        break;
    case "Large":
        Console.WriteLine("The price is $10.");
        break;
    default:
        Console.WriteLine("Invalid size selected.");
        break;
}

Here, the program will print "The price is $10." since the selected size is "Large."

Build a Simple Application Using `switch-case`

Let’s build a simple calculator application that performs basic arithmetic operations like addition, subtraction, multiplication, and division based on user input.

csharp

using System;

public class SimpleCalculator
{
    public static void Main(string[] args)
    {
        Console.WriteLine("Enter first number:");
        double num1 = Convert.ToDouble(Console.ReadLine());

        Console.WriteLine("Enter operator (+, -, *, /):");
        char operation = Console.ReadLine()[0];

        Console.WriteLine("Enter second number:");
        double num2 = Convert.ToDouble(Console.ReadLine());

        switch (operation)
        {
            case '+':
                Console.WriteLine($"Result: {num1 + num2}");
                break;
            case '-':
                Console.WriteLine($"Result: {num1 - num2}");
                break;
            case '*':
                Console.WriteLine($"Result: {num1 * num2}");
                break;
            case '/':
                if (num2 != 0)
                {
                    Console.WriteLine($"Result: {num1 / num2}");
                }
                else
                {
                    Console.WriteLine("Cannot divide by zero.");
                }
                break;
            default:
                Console.WriteLine("Invalid operator.");
                break;
        }
    }
}

Explanation:

The user is prompted to enter two numbers and an arithmetic operator.
Based on the operator (+, -, *, /), the corresponding calculation is performed.
The default case handles invalid operators.