How to cast Entity framework Objects in Web API? - asp.net-mvc-4

Question

I'm using entity framework and I figured out that it ain't able to serialize the output of
EDM Objects. For now I'm using Northwind Products-table. SO thereforth I'm forced to cast the Object to another and are using the .Cast but it doesn't work.
The only solution I have is to property by property do it manually in my code, but I'm thinking - there must be a better way!
For god's sake - it is 2013! And this Entity seems like a good idea in the beginning but it has so many gotchas and constraints that it actually hinders more than it helps, but anyway the EDMX diagrams are nice!
Anybody who has a better solution to casting the objects?
POCO
public class Product
{
public int ProductID { get; set; }
public string ProductName { get; set; }
//public Nullable<int> SupplierID { get; set; }
//public Nullable<int> CategoryID { get; set; }
public string QuantityPerUnit { get; set; }
public Nullable<decimal> UnitPrice { get; set; }
public Nullable<short> UnitsInStock { get; set; }
public Nullable<short> UnitsOnOrder { get; set; }
public Nullable<short> ReorderLevel { get; set; }
//public bool Discontinued { get; set; }
public Category Category { get; set; }
//public ICollection<Order_Detail> Order_Details { get; set; }
//public Supplier Supplier { get; set; }
}
View Model
public class ProductsViewModel
{
public List<POCO.Product> Products { get; set; }
public ProductsViewModel()
{
using (NorthwindEntities dNorthwindEntities = new NorthwindEntities())
{
this.Products = dNorthwindEntities.Products.Cast<POCO.Product>().ToList();
Web api controller:
public class ProductsController : ApiController
{
public List<Product> GetAllProducts()
{
var viewmodel = new ProductsViewModel();
return viewmodel.Products;
}

Answer 1

1.
You can use frameworks like AutoMapper to handle Entities to ViewModel / DTO mapping automatically.
2.
Using Entities in the View (even in their POCO form) is not recommended for couple of reasons:
Security: Sending entities back to the client/view may expose more data than you intended.
Serialization: Since your entities usually contain reference to another entities and those entities may contain a reference back to the (parent) entity, you have to configure your serializer to handle this situation otherwise you'll get Circular Dependency Exception.
Incompatibility: The structure of your entity may not be compatible with what your view/client needs to render itself. Sometimes your view just needs a simple string while the entity holds this data in a much complex way hence the view needs to 'extract' it and you end up with a view full of unnecessary entity-drill-down code.