title: Update datatables using relation
body: <p>I try to update two tables using a relation and table adapters generated in dataset designer. But unable to perform child table update, it is not inserted, the problem is that during child table update the identity column value is unknown.
  Table "Users" has primary key and identity column UserId. Table "UserInRoles" has column UserId and foreign key to Users.UserId. Here is my code:</p>
  
  <pre><code>usersTableAdapter.Fill(ds.Users);
  userInRolesTableAdapter.Fill(this. ds.UserInRoles);
  DataRow userRow = ds.Users.NewRow();
  userRow["UserName"] = userName; // and fill other userRow fields.
  DataRow userRoleRow = ds.UserInRoles.NewRow();
  userRoleRow["RoleId"] = selectedRole; // leave unfilled column "UserId", because I thing the relational update should do it.
  
  userRoleRow.SetParentRow(userRow, ds.Relations["FK_UserInRoles_Users"]);
  ds.Users.Rows.Add(userRow);
  ds.UserInRoles.Rows.Add(userRoleRow);
  
  tableAdapterManager.UpdateAll(ds);
  ds.AcceptChanges();
  //usersTableAdapter.Update(ds.Users);
  //userInRolesTableAdapter.Update(ds.UserInRoles);
  </code></pre>
  
  <p>I set both relation type, update rule: cascade, delete rule: cascade, accept rule: none. Refresh the datatable option is selected. On database the foreign key is set to cascade update too, and enforce for replication and enforce foreign key to yes.
  What I am doing wrong?
  I tried Users.GetChanges() after users table update, but don't get any changes. The only way it works now is to fill again users table after update. Tried update table adapters separately, but then get error violating foreign key.</p>