C# Feature – Init-only setters

Overview

init enables immutable patterns by allowing property initialization in object initializers while preventing later mutation.

Introduced In

C# 9 (2020)

Before

public class Person { public string Name { get; private set; } }

After

public class Person { public string Name { get; init; } }
var p = new Person { Name = "Ada" };

Annotated Example

public record User(string Id)
{
  public string Email { get; init; }
}

Gotchas & Best Practices

• Combine with records for immutable data models.

Related Features

• Required members
• Auto-implemented properties
• Properties & Events

Version history

• C# 9: init introduced for object initializers.