Eric Campbell Jan 30, 2025 1 min read C#

C# Pattern Matching: Beyond Simple Switch Statements

Pattern matching in modern C# eliminates verbose type checking and casting, making control flow more expressive.

Key Insights

Switch expressions with patterns replace chains of if/else type checks
Property patterns let you match on object shape without destructuring
List patterns in C# 11 enable concise array/list matching

Switch Expressions

string Describe(object obj) => obj switch
{
    int n when n < 0 => "negative",
    int n => $"positive: {n}",
    string s => $"text: {s}",
    null => "nothing",
    _ => "unknown"
};

Property Patterns

decimal CalculateDiscount(Order order) => order switch
{
    { Total: > 1000, Customer.IsPremium: true } => 0.20m,
    { Total: > 500 } => 0.10m,
    { Customer.IsPremium: true } => 0.05m,
    _ => 0m
};

List Patterns (C# 11)

var result = numbers switch
{
    [1, 2, 3] => "exact match",
    [1, .., 3] => "starts with 1, ends with 3",
    [_, _, _] => "exactly three elements",
    [] => "empty",
    _ => "other"
};