Lesson 16 of 40 Core C# Intermediate ⏱ 30 min

Pattern Matching & Switch Expressions

Write elegant conditional logic using C#'s powerful pattern matching — type patterns, property patterns, list patterns, and exhaustive switch expressions.

Part 1: Type & Property Patterns

object shape = GetShape();
double area = shape switch
{
    Circle { Radius: var r } => Math.PI * r * r,
    Rectangle { Width: var w, Height: var h } => w * h,
    null => throw new ArgumentNullException(),
    _ => throw new NotSupportedException()
};

Part 2: List Patterns (C# 11+)

int[] nums = [1,2,3];
var desc = nums switch
{
    [] => "empty",
    [var x] => $"single: {x}",
    [var first, .., var last] => $"first={first}, last={last}",
};

Part 3: Relational & Logical Patterns

string ClassifyAge(int age) => age switch
{
    < 0 => throw new ArgumentOutOfRangeException(),
    <= 12 => "Child",
    > 12 and <= 17 => "Teenager",
    >= 65 => "Senior",
    _ => "Adult"
};

Part 4: Pattern Matching with is

// Declaration pattern
if (obj is string { Length: > 0 } s)
Console.WriteLine($"Non-empty string: {s}");

// Negation pattern
if (obj is not null and not string)
Console.WriteLine("Not null and not a string");

Pattern Matching & Switch Expressions

Part 1: Type & Property Patterns

Part 2: List Patterns (C# 11+)

Part 3: Relational & Logical Patterns

Part 4: Pattern Matching with is

C# in Visual Studio 2026