Init-Only Setters (`init`), `required` Keyword & Object Initializers

1Concept

`init` accessors allow property mutation only during object construction. The `required` keyword forces callers to initialize specified properties in object initializers at compile-time.

2Architecture Diagram

Caller Construction:
var config = new ServerConfig { Host = "localhost", Port = 8080 }; // OK
config.Port = 9000; // COMPILE ERROR: init-only property cannot be mutated after construction!

3Code Example

using System;

public class ServerConfig
{
    public required string Host { get; init; }
    public required int Port { get; init; }
    public bool EnableSsl { get; init; } = true;
}

public class InitOnlyDemo
{
    public static void Main()
    {
        var cfg = new ServerConfig
        {
            Host = "api.enterprise.cloud",
            Port = 443
        };

        Console.WriteLine($"Server: {cfg.Host}:{cfg.Port} (SSL: {cfg.EnableSsl})");
    }
}

4Expected Output

Server: api.enterprise.cloud:443 (SSL: True)

5Key Takeaways

• ✓`init` enables clean object initializers while maintaining immutability.
• ✓`required` guarantees that critical properties are never omitted during instantiation.
• ✓Combine with `[SetsRequiredMembers]` for custom constructor overloads.