C# Feature - readonly struct

Overview

readonly struct marks a value type as immutable so the compiler can enforce that instance members do not mutate state.

Introduced In

C# 7.2 (2017)

Before

public struct Distance
{
  public double Meters { get; }
}

After

public readonly struct Distance
{
  public double Meters { get; }
  public Distance(double meters) => Meters = meters;
}

Gotchas & Best Practices

• Use readonly struct for small immutable value objects.
• Mutable fields defeat the purpose and should be avoided.