avoid datagrid rows multiplied in master-detail datagrid

Question

I have Master-Detail datagrid in my application created using Linq to Entities. I would like to display the selected row's deatils of the Master datagrid on the details datagrid.

what I have tried 

 
     private void Page_Loaded(object sender, RoutedEventArgs e)
        {
            this.db = new DB_ProdEntities();
            var serverQuery = from a in this.hmdb.Servers
                              orderby a.ServerID
                              select a;
          dgServer.ItemsSource = null;           
          dgServer.ItemsSource = serverQuery;
      }

      private void dgServer_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            string serverID = (dgServer.SelectedItem as Server).Name;
          
            var componentQuery = from a in db.Components
                                 where a.ServerID == serverID
                                 orderby a.Name
                                select a;
          dgComponent.ItemsSource = null;        
          dgComponent.ItemsSource = componentQuery;
        }

OUTPUT:

when I select the first row everything is normal, but when I select the second row it displays the details along with the selection of the first row's details like this

Output 1

http://postimg.org/image/9x1f616n7/

Output 2
http://s16.postimg.org/4nylei9ph/op2.png

how to overcome this problem?