using ComboBox with Linq to Sql and relationships

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C#

LINQ

Hi,

I am trying to update a field in one table using values from another,
i have successfully achieved data binding, if the foreign key is linked to a primary key in the same table, but cannot seem to get it to work on relational tables,

dbs = new dbConnDataContext();

var userGrouping =
  from c in dbs.UserGroupings
  select c;

var group =
    from c in dbs.Groups
    select c;
//this is a data navigation bar
navUserGroupings.DataSource = userGrouping;

groupComboBox.DataSource = group;
groupComboBox.DisplayMember = "GroupName";
groupComboBox.ValueMember = "ID";
groupComboBox.DataBindings.Add("SelectedValue", userGrouping, "GroupID", true, DataSourceUpdateMode.OnPropertyChanged, 0);

Everytime i submit changes, it inserts 0 regardless of the value i select


Thanks.