Create and use Value Objects

Create a new value object by decorating a partial type with the ValueObject attribute:

[ValueObject<int>] 
public partial struct CustomerId { }

The type must be partial as the source generator augments the type with another partial class containing the generated code.

Now, create a new instance by using the From method:

var customerId = CustomerId.From(42);

If you try to use the constructors, the analyzer rules will catch this and stop you.

You can now be more explicit in your methods with signatures such as:

public void HandlePayment(
    CustomerId customerId, 
    AccountId accountId, 
    PaymentAmount paymentAmount)

If your type has validation, then the From method will throw an exception if validation fails.

This stops invalid instances being created, but exceptions might not be desirable. In this case, use the TryFrom method. There are two overloads for this. One returns a ValueObjectOrError<T> and one returns a bool and takes an out parameter.

Last modified: 16 September 2024