Can an ApiController return an object with a collection of other objects?

Question

If I have a `Customer` class that just has simple properties (e.g. `Name`, etc.) then I can create a `CustomersController` that derives from `ApiController`, and query my Customer objects using the URL `/api/customers`. Similarly, if I have an `Order` class with simple properties (`Description`, `Amount`) then I can create an `OrdersController` and access it in the same way. However, if I then add a property to my `Customer` class that lists the `Order`s associated with that `Customer`: ``` public class Customer { public int Id { get; set; } public string Name { get; set; } // ... public virtual ICollection<Order> Orders { get; set; } } ``` ...then when I try to query using `/api/customers` I get a 500 Server Error. I can put a breakpoint within the `CustomersController` and can see that it does call the correct method, and attempts to return a value. However, somewhere in the guts of the framework it fails to turn that into an HTTP response. It looks like it cannot serialize the `Ord…

Accepted Answer

You are passing an Entity Framework entity which will cause problems. You need Data Transfer Objects to pass and receive your data. Because you bind entities together, it won't allow you to serialize the data.

Can an ApiController return an object with a collection of other objects?

Solution

Problem