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Lesson 4318 min read

Pattern Matching

Learn C#'s pattern matching features — type patterns, property patterns, and relational patterns.

What is Pattern Matching?

Pattern matching lets you test a value against a shape or condition, and extract data from it, all in one concise expression. It has grown into one of C#'s most powerful modern features.

Type Patterns

object value = 42;


if (value is int number)
{
    Console.WriteLine($"It's an int: {number}");
}


string Describe(object obj) => obj switch
{
    int i => $"Integer: {i}",
    string s => $"String: {s}",
    null => "Nothing",
    _ => "Unknown type"
};


Console.WriteLine(Describe(42));
Console.WriteLine(Describe("hello"));
Output

Click Run to see what this code prints.

Property Patterns

You can match against an object's property values directly, without writing separate if-checks.

record Order(string Status, decimal Total);


string Describe(Order order) => order switch
{
    { Status: "Cancelled" } => "This order was cancelled.",
    { Total: > 1000 } => "This is a high-value order.",
    _ => "Standard order."
};


Console.WriteLine(Describe(new Order("Active", 1500)));
Output

Click Run to see what this code prints.

Relational Patterns

Since C# 9, you can use comparison operators directly inside patterns.

string Grade(int score) => score switch
{
    >= 90 => "A",
    >= 70 => "B",
    >= 50 => "C",
    _ => "F"
};


Console.WriteLine(Grade(85));
Output

Click Run to see what this code prints.

FAQs

Very commonly with switch expressions for classification logic, and with `is` for safe type-checking before casting an object.

Summary

  • `is` and switch expressions support type, property, and relational patterns.
  • Property patterns let you match directly on an object's field values.
  • Relational patterns (>=, <, etc.) work directly inside switch cases.
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