Linq sql数据绑定到winforms组合框

I am trying to bind a ComboxBox to a foreign key table. I know that on cannot bind to the actual foreign key, SomeTableClassFK, (causes a LinqSql exception when the FK already has a value). So, I am binding to FK object, SomeTable, reference thru the SelectedItem property of the ComboBox. I am trying to bind a ComboxBox to a foreign ke