C# Switch Case
Introduction
The switch statement in C# provides a cleaner, more readable alternative to multiple if-else statements when checking a single variable against multiple possible values. It's particularly useful when you need to execute different code blocks based on the value of a single expression.
Unlike multiple if-else statements, a switch statement can be more efficient and easier to read, especially when dealing with many possible conditions based on a single variable.
Basic Syntax
Here's the basic syntax of a C# switch statement:
switch (expression)
{
case value1:
// Code to execute if expression equals value1
break;
case value2:
// Code to execute if expression equals value2
break;
// More case statements as needed
default:
// Code to execute if expression doesn't match any case
break;
}
Let's explore each component:
- expression: The variable or expression being evaluated
- case value: A constant value to compare against the expression
- break: Terminates the switch block (required at the end of each case)
- default: Optional case that executes when no other cases match
Simple Example
Let's start with a basic example that determines the name of a day based on a number:
int dayNumber = 3;
string dayName;
switch (dayNumber)
{
case 1:
dayName = "Monday";
break;
case 2:
dayName = "Tuesday";
break;
case 3:
dayName = "Wednesday";
break;
case 4:
dayName = "Thursday";
break;
case 5:
dayName = "Friday";
break;
case 6:
dayName = "Saturday";
break;
case 7:
dayName = "Sunday";
break;
default:
dayName = "Invalid day number";
break;
}
Console.WriteLine($"Day {dayNumber} is {dayName}");
Output:
Day 3 is Wednesday
The break Keyword
Each case section must end with a break statement (or another jump statement like return or goto). The break statement prevents "falling through" to the next case, which would execute the code in the next case regardless of whether that case's condition was met.
If you forget to include a break, the compiler will generate an error.
The default Case
The default case is optional and handles situations where the expression doesn't match any of the defined cases. It's similar to the else clause in an if-else statement chain.
char grade = 'X';
string message;
switch (grade)
{
case 'A':
message = "Excellent!";
break;
case 'B':
message = "Good job!";
break;
case 'C':
message = "Satisfactory";
break;
case 'D':
message = "Passed";
break;
case 'F':
message = "Failed";
break;
default:
message = "Invalid grade";
break;
}
Console.WriteLine(message);
Output:
Invalid grade
Multiple Case Labels
You can have multiple case labels for the same code block when you want the same action for different values:
char choice = 'Y';
bool continueProgram;
switch (choice)
{
case 'Y':
case 'y':
continueProgram = true;
break;
case 'N':
case 'n':
continueProgram = false;
break;
default:
Console.WriteLine("Invalid choice. Defaulting to No.");
continueProgram = false;
break;
}
Console.WriteLine($"Continue program: {continueProgram}");
Output:
Continue program: True
Switch Expressions (C# 8.0+)
C# 8.0 introduced an enhanced form called "switch expressions" that is more concise for simple cases:
int dayNumber = 3;
string dayName = dayNumber switch
{
1 => "Monday",
2 => "Tuesday",
3 => "Wednesday",
4 => "Thursday",
5 => "Friday",
6 => "Saturday",
7 => "Sunday",
_ => "Invalid day number"
};
Console.WriteLine($"Day {dayNumber} is {dayName}");
Output:
Day 3 is Wednesday
Note that:
- The syntax uses
=>instead of colons andbreakstatements - The
_(underscore) replaces thedefaultkeyword - The entire switch is an expression that returns a value
Pattern Matching in Switch Statements
C# 7.0 and later versions allow you to use patterns in switch statements, enhancing their power:
Type Patterns
object item = "Hello";
switch (item)
{
case int i:
Console.WriteLine($"Item is an integer with value {i}");
break;
case string s:
Console.WriteLine($"Item is a string with value \"{s}\"");
break;
case bool b:
Console.WriteLine($"Item is a boolean with value {b}");
break;
case null:
Console.WriteLine("Item is null");
break;
default:
Console.WriteLine($"Item is of type {item.GetType()}");
break;
}
Output:
Item is a string with value "Hello"
When Clauses
You can add when clauses to case statements to add additional conditions:
int score = 85;
switch (score)
{
case int n when n >= 90:
Console.WriteLine("Grade: A");
break;
case int n when n >= 80:
Console.WriteLine("Grade: B");
break;
case int n when n >= 70:
Console.WriteLine("Grade: C");
break;
case int n when n >= 60:
Console.WriteLine("Grade: D");
break;
default:
Console.WriteLine("Grade: F");
break;
}
Output:
Grade: B
Real-World Application: Simple Calculator
Let's implement a simple calculator using a switch statement:
double a = 10;
double b = 5;
char operation = '+';
double result = 0;
switch (operation)
{
case '+':
result = a + b;
break;
case '-':
result = a - b;
break;
case '*':
result = a * b;
break;
case '/':
if (b != 0)
result = a / b;
else
{
Console.WriteLine("Error: Division by zero");
return;
}
break;
default:
Console.WriteLine("Error: Invalid operation");
return;
}
Console.WriteLine($"{a} {operation} {b} = {result}");
Output:
10 + 5 = 15
Real-World Application: Menu System
Here's how you might use a switch statement to build a simple menu system:
Console.WriteLine("Simple Menu System");
Console.WriteLine("1. View Profile");
Console.WriteLine("2. Edit Settings");
Console.WriteLine("3. Help");
Console.WriteLine("4. Exit");
Console.Write("Enter your choice (1-4): ");
int choice = int.Parse(Console.ReadLine());
switch (choice)
{
case 1:
Console.WriteLine("Loading profile...");
// Code to load profile would go here
break;
case 2:
Console.WriteLine("Opening settings...");
// Code to open settings would go here
break;
case 3:
Console.WriteLine("Displaying help...");
// Code to display help would go here
break;
case 4:
Console.WriteLine("Exiting program...");
// Code to exit would go here
break;
default:
Console.WriteLine("Invalid choice. Please select a number between 1 and 4.");
break;
}
When to Use Switch vs. If-Else
Use a switch statement when:
- Testing a single variable against multiple known values
- You have many possible execution paths based on one variable
- You want more readable code with many conditions
Use if-else statements when:
- Testing multiple different variables
- Using complex conditions that can't easily be represented as constant cases
- You only have a few conditions to check
Common Mistakes and Best Practices
-
Forgetting break statements: Always include
break(or another jump statement) at the end of each case. -
Order matters in pattern matching: More specific cases should come before general ones, especially when using when clauses.
-
Switch expressions vs. statements: Use switch expressions for simple value assignments; use switch statements for more complex logic.
-
Default case: It's a good practice to include a default case to handle unexpected values.
-
Readability: Keep case statements short. Consider extracting complex logic into separate methods.
Summary
The switch statement in C# provides a powerful and readable way to handle multiple branching paths based on a single value. It offers several advantages over multiple if-else statements, including improved readability and potential performance benefits.
C# has enhanced the switch statement with pattern matching, switch expressions, and when clauses, making it even more useful in modern programming.
Exercises
-
Create a program that converts numeric month values (1-12) to month names.
-
Write a switch statement that categorizes characters as vowels, consonants, digits, or special characters.
-
Create a simple role-based menu system where different options are presented depending on whether the user is an "admin", "manager", or "user".
-
Convert a series of if-else statements to a switch statement, and vice versa.
Additional Resources
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