Prerequisites:
Windows forms combobox
1) DropDownStyle = DropDown (allows typing in)
2) AutoCompleteMode = SuggestAppend
3) Populated from a DataTable directly in code. ValueMember = "ID" which is int type, and DisplayMember = "Name" which is string type.
4) SelectedValue is bound to an int (or can be Nullable<int>) type property of a business object, through a BindingSource object.
Required:
Pass null to the property of the business object if the user input doesn't match any value in the list of the combobox. In case, business object's property is int type (not Nullable<int>), business object should throw an error.
The Problem:
The combobox or the BindingSource object doesn't try to pass null to the property of the business object, if a selection or entry doesn't match any value in the list of the combobox, even though it sets its SelectedValue to null.
What might be wrong