I get the error:
Ambiguous match found
During this code on the .Add
var db = new NexusEntities();
db.Reports.Ad
This is a "weakness" in EF. It happens when the same property appears in class / subtype hierarchy.
Most likely you have a hidden field. i.e. a property that has been redefined. When EF looks for the a property it too must use the type/base tree to find the property. But if it finds it twice in the tree, it interprets this as a duplicate. EF doesnt just use the lowest most specific override.
So property hiding is not possible with EF.
Check your classes, a property will occur twice somewhere.