How Do I Create An TreeCollectionbased For Combobox.Itemtemplate?

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C#

WPF

C#4.0

hi there. i have following XAML code:

<ComboBox x:Name="MainComboBox" Height="35" Width="250" removed="WhiteSmoke" BorderBrush="Gray"
                  IsEditable="True" TextSearch.TextPath="Name" TextBoxBase.TextChanged="MainComboBox_TextChanged">
            <ComboBox.Resources>
                <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Transparent"/>
                <SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}" Color="Transparent"/>
            </ComboBox.Resources>
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TreeView BorderBrush="Transparent" BorderThickness="0" ItemsSource="{Binding RelativeSource={RelativeSource AncestorType={x:Type ComboBox}, Mode=FindAncestor}, Path=ItemsSource}">
                        <TreeView.ItemTemplate>
                            <HierarchicalDataTemplate ItemsSource="{Binding Children}" DataType="{x:Type data:SubscriberGroupModel}">
                                <CheckBox Content="{Binding Name}" Height="25" Width="80" />
                            </HierarchicalDataTemplate>
                        </TreeView.ItemTemplate>
                    </TreeView>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox> 

and my code behind:

private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            List<SubscriberGroupModel> list = SubscriberGroupDB.GetCustomSubscriberGroup();
            MainComboBox.ItemsSource = list;
        } 

this control doesn't work properly because it produces itms more than once.
my query s correct.
please help me.
thanks alot