External Content type linq error

I have a list with an externa content type.

I am tring to fetch the element by server side code, but i get this exception:

Microsoft.BusinessData.Infrastructure.BdcException

This is my code:

SPList myList = Web.Lists["listaName"];
SPListItem item = (from SPListItem item in myList.Items
                      where Convert.ToString(item["BdcIdentity"]) == myID
                      select item).ToList().FirstOrDefault();