# Classes and Records — .NET Core: Build, Test and Ship Web APIs

Source: https://www.geekswithgeeks.com/en/dotnet-core/cs-classes-records

> Model data with classes and immutable records, and compare them correctly.

## Class or record?

A `class` compares by reference by default. A `record` compares by value and gives you `with` copies and a readable `ToString()`. Use records for plain data such as API request and response shapes.

## A record in action

Two records with equal values are equal. `with` makes a changed copy and leaves the original untouched.

```csharp
public record Product(int Id, string Name, decimal Price);

var a = new Product(1, "Pen", 10m);
var b = new Product(1, "Pen", 10m);
Console.WriteLine(a == b);
var c = a with { Price = 12m };
Console.WriteLine(c);
```

Output:

```
True
Product { Id = 1, Name = Pen, Price = 12 }
```

## Cheque vs address

Comparing classes by reference is like asking whether two people live at the same address. Comparing records by value is like asking whether two cheques show the same amount and payee.

**Quiz:** Which keyword makes a modified copy of a record?

- [ ] copy
- [x] with
- [ ] clone
- [ ] new

*Answer:* with. `with { ... }` creates a new record with the listed properties changed.