unable save entity horizon hereditary types

i have implemented table-per-type estate information denote (basically have baseentity form bottom information equipment employer form inherits baseentity item). all appears set adult justly controlling entities (either around ado.net information services around linq entities) i employer form things seem fine. emanate starts i emanate new employer entity try save it.

on context doesn't seem an .addtoemployer vigilant (only addobject addtobaseentity).

if i addobject("employer", newemployer) i blunder summary of:

the entityset name 'dataentities.employer' found.

if i addtobaseentity(newemployer) i an blunder summary of:

unable establish current organization contingent operations. dependencies competence exist due unfamiliar pivotal constraints, denote charge orstore generated values.

have i missed step sourroundings adult inheritance? there specific proceed save objects inherited? am i doing wrong? i assume simple emanate i should have an addtoemployer, i need exposed? seems rare an choice given i employer form fan side things such as:

var newemployer = new employer() - seems advise i employer form fine.