wpf listview 绑定问题


我在listview中绑定了四列数据，第三列用combobox来显示。现在的问题是：绑定成功了，能够显示数据，但是当选择combobox时，无法改变combobox的值，请帮忙看看是什么问题？
xaml：
                            <ListView.View>
                                <GridView>
                                        <GridViewColumn Header="硬件ID" Width="220" DisplayMemberBinding ="{Binding Path=CamID}"/>
                                        <GridViewColumn Header="当前通道" Width="140" DisplayMemberBinding="{Binding Path = CurChannel}"/>
                                        <GridViewColumn Header="设置通道" Width="140">
                                            <GridViewColumn.CellTemplate>
                                                <DataTemplate>
                                                    <ComboBox Height="23" HorizontalAlignment="Left" Name="cmbSetChannel" VerticalAlignment="Top" Width="102" Text="{Binding Path = SetChannel, Mode=TwoWay}" IsEnabled="True" IsEditable="True" IsReadOnly="True">
                                                        <ComboBoxItem Content="通道1" />
                                                        <ComboBoxItem Content="通道2" />c# 绑定测试：
 ObservableCollection<CameraConfig> listCamConfig =new ObservableCollection<CameraConfig >();
                        for (int i = 0; i <= 3; i++)
                        {
                            CameraConfig ccfg = new CameraConfig("d:\abc", "abcdddd", "通道2", "通道1", "3D");
                            listCamConfig.Add(ccfg);
                        }
                        this.lvCamLocat.ItemsSource = listCamConfig;结果界面combobox的值无法改变。