C# Record vs. Class: Key Differences and Best Use Cases

When developing in C#, choosing between records and classes depends on the behavior and design of your data structures. Let’s explore their key differences, along with some practical examples.

What Are C# Records?

Records were introduced in C# 9.0 as a way to define immutable, data-centric types. Records focus on representing data rather than functionality.

By default, records use value-based equality, meaning two records with the same property values are considered equal, even if they are different instances. This behavior is helpful when dealing with data structures where the data values define equality.

public record Person(string name, int age);

var person1 = new Person("Alice", 30);
var person2 = new Person("Alice", 30);

// This will return true because the properties are identical
bool areEqual = person1 == person2;

What Are C# Classes?

Classes, on the other hand, are reference types that use reference-based equality by default. Two class instances are only considered equal if they reference the same object in memory. Unlike records, classes are typically mutable, allowing changes to their properties after instantiation.

public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

var person1 = new Person { Name = "Alice", Age = 30 };
var person2 = new Person { Name = "Alice", Age = 30 };

// This will return false because person1 and person2 reference different objects
bool areEqual = person1 == person2; 

When to Use Records

• Immutability: Use records when you want to create types that represent fixed data. This is especially useful for data transfer objects (DTOs) or entities that should not change after creation.
• Value Semantics: Ideal when equality should be based on property values rather than object references.
• Data Structures: Great for simple data structures, configurations, or results of computations where data encapsulation and consistency are crucial.

public record Order(string product, decimal price);

When to Use Classes

• Mutability: Use classes when objects need to have properties that can change over time.
• Complex Behavior: Ideal for types that include complex methods, events, or lifecycle management.
• Inheritance: If you need to implement polymorphic behavior with a class hierarchy, classes are the way to go.

public class Car
{
    public string Model { get; set; }
    public int Year { get; set; }
    
    public void StartEngine()
    {
        Console.WriteLine("Engine started!");
    }
}

Key Takeaways

• Records offer immutability and value-based equality, making them suitable for representing fixed data structures.
• Classes provide flexibility with mutability and reference-based equality, suited for scenarios where the object’s state changes.

Choosing between records and classes comes down to your specific use case. If you need an immutable data container with value semantics, go for records. If your type involves behavior, mutability, or complex interactions, a class is usually the better choice.