C# Records

Introduced in C# 9, Records are a concise way to define reference types with built-in functionality for encapsulating data. They provide value-based equality and are primarily used for immutable data models.

Key Features

1. Value Equality

Unlike standard classes (which use reference equality), two record instances are equal if all their properties match.

public record Person(string FirstName, string LastName);
var p1 = new Person("Jane", "Doe");
var p2 = new Person("Jane", "Doe");
bool areEqual = (p1 == p2); // True

2. Immutability (Init-Only)

Positional records use init properties by default, making them ideal for high-signal tool inputs where state should not change after instantiation.

3. Nondestructive Mutation (`with` expression)

Allows creating a new record based on an existing one with specific changes.

var p3 = p1 with { FirstName = "John" };

Agentic Use Case

Records are the preferred structure for Tool Inputs in .NET. Their immutability and value-based identity make them predictable and easy to cache in an agent's memory.