In database I have a table with user information (name, last name, ...). One of the fields are DepartamentID (type - integer) - it's a relationship to another table - Departaments. Departaments table has primary key DepartamentID.
In *.xaml file i've defined a combobox: <ComboBox
Name="comboBox"
DisplayMemberPath="Name"
SelectedValuePath="DepartamentID"
SelectedValue="{Binding DepartamentID}"
IsSynchronizedWithCurrentItem="True"
/>

I have binding a one table entity to comboBox's parent, and to get comboBox items source i use this: comboBox.ItemsSource = db.Departaments.ToList<Departament>(). ComboBox content loads fine and selected element also is correct, but, when I try to choose another item from comboBox, I'm getting ForeignKeyReferenceAlreadyHasValueException. What I should do in this situation?