c# - Modelling a nullable foreign key Entity Framework -

take following pseudocode database

table foo {     fooid int not null,     name varchar not null }  table bar {     barid int not null,     name varchar not null }  table waa {     waaid int not null,     name varchar not null }  table link {     linkid int not null,     fooid int null,     barid int null,     waaid int null,     description varchar not null } 

the purpose of link table allow me link entities in single table, without having multiple foo_bar_link, foo_waa_link etc. tables.

i moddeling db in entityframework v5. such, want able specify 1 many relationship between foo , link, can links associated given foo.

problem
entityframework designer lets one-many relationships exist foreign key not null. want foo have navigation property associations gets of association entities fooid = foo.fooid. note, using designer.

ef not designed support unusual models yours. way know insert "empty" meaning rows example id equals -1. in business logics or in dto implement "clever" getter , setter.