This is happening when I try to create the entity using a Create style action in Asp.Net MVC 2.
The POCO has the following properties:
public int Id
The Id should be sent from the client as 0. The model does not have a problem with Id=0, this is the default of int. The problem is that he does not see the value coming from the client or it's coming with space or null. I have an input hidden that represents the Id (or in complex object NestedPropertyId/NestedProperty.Id) so I make sure it starts with a value of zero.
Also when Ireset the form to Add New entity in the client side, I make sure to initialize the hidden with zero.
Hope this helps somone.
Efy