Switch Expression in C# 8.0

Switch expressions in C# were introduced in C# 8.0. They are a more concise, readable and expressive way to handle multiple conditional branches compared to the traditional switch statement. Switch expressions can return values directly, making them suitable for assignments, return statements or inline logic.

It differs from the traditional switch statement in the following ways:

• Returns a value directly.
• Uses expression syntax instead of statements.
• Eliminates the need for break or return in each branch.
• Supports pattern matching, including type patterns, property patterns and relational patterns.

Syntax

C#

var result = input switch
{
    pattern1 => expression1,
    pattern2 => expression2,
    _ => defaultExpression
};

• input is the value being matched.
• pattern can be a constant, type, relational condition or property pattern.
• _ acts as the default case, matching any unmatched values.

Example: Simple Switch Expression

C#

int number = 3;

string description = number switch
{
    1 => "One",
    2 => "Two",
    3 => "Three",
    _ => "Unknown"
};

Console.WriteLine(description); // Output: Three

Here, number switch directly returns a string based on the value of number.

Example: Pattern Matching in Switch Expressions

C#

object obj = 42;

string typeDescription = obj switch
{
    int i => $"Integer: {i}",
    string s => $"String: {s}",
    null => "Null value",
    _ => "Other type"
};

Console.WriteLine(typeDescription); // Output: Integer: 42

This demonstrates type patterns and the default _ case for unmatched types.

Example: Using Relational Patterns

C#

int score = 85;

string grade = score switch
{
    >= 90 => "A",
    >= 80 => "B",
    >= 70 => "C",
    >= 60 => "D",
    _ => "F"
};

Console.WriteLine(grade); // Output: B

Relational patterns allow concise comparison logic directly within the switch expression.

When to Use Switch Expressions

• When you need a concise value-based mapping from an input.
• When using pattern matching for cleaner and more readable code.
• When you want to avoid fall-through bugs common in switch statements.

Suggested Quiz

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3 Questions

Which of the following is a key difference between a switch expression and a traditional switch statement in C#?

• A

  Switch expressions require break statements

• B

  Switch expressions cannot return values

• C

  Switch expressions return a value directly

• D

  Switch expressions do not support pattern matching

Explanation:

Unlike traditional switch statements, switch expressions return a value directly, making them ideal for assignments and return statements without requiring break or explicit return keywords in each case.

What is the purpose of the underscore (_) in a switch expression?

• A

  It represents a null value

• B

  It matches only numeric values

• C

  It is used for type casting

• D

  It acts as the default case

Explanation:

Which switch expression correctly uses relational patterns to assign a grade?

• A
  C#

  string grade = score switch
  {
      score >= 90 => "A",
      score >= 80 => "B",
      _ => "F"
  };
  

• B
  C#

  string grade = switch(score)
  {
      >= 90: "A",
      >= 80: "B"
  };
  

• C
  C#

  string grade = score switch
  {
      >= 90 => "A",
      >= 80 => "B",
      _ => "F"
  };
  

• D
  C#

  string grade = score => switch
  {
      >= 90 => "A",
      >= 80 => "B"
  };
  

Explanation:

Relational patterns are used directly in the pattern position (>= 90, >= 80) and must follow the correct switch expression syntax with => and a fallback _ case.

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