C# Feature - List patterns

Overview

List patterns let pattern matching inspect the length and element layout of a sequence in one expression.

Introduced In

C# 11.0 (2022)

Before

if (numbers.Length == 3 && numbers[0] == 1 && numbers[2] == 3)
{
  Console.WriteLine("match");
}

After

if (numbers is [1, _, 3])
{
  Console.WriteLine("match");
}

Gotchas & Best Practices

• Use list patterns for sequence shape checks, not heavy data processing.
• Combine them with slice patterns only when readability stays strong.