Pattern Matching in C# - Example You Can Run Online

Introduction

Patterns combine type checks, extraction, and conditions without unsafe casts.

The switch expression handles null, positive integers, non-empty strings, and a final fallback in one exhaustive expression.

See how it works

Move the slider to change the day. The program jumps straight to the matching case, and to the default case when nothing matches.

Runnable C# example

C#

Run code →

Program.cs

using System;

class Program
{
    static string Describe(object? value) => value switch
    {
        null => "missing",
        int number when number > 0 => $"positive {number}",
        string { Length: > 0 } text => $"text: {text}",
        _ => "other"
    };

    static void Main() => Console.WriteLine(Describe(12));
}

Result of running the code

positive 12

Practice with the debugger

Set a breakpoint on an important assignment or condition, click Debug, and inspect the local values before stepping to the next line.

Practice with a challenge

Use what this lesson covers to solve a real problem. Each challenge runs in your browser with instant tests and an AI review.

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