WPF DataGrid 每行ComboBox 内容不同的设置方法

<toolkit:DataGridComboBoxColumn x:Name="DgCbcSignal" Header="信号源" 
                                                        SelectedItemBinding="{Binding SelectedSignal}" 
                                                        >
                            <toolkit:DataGridComboBoxColumn.ElementStyle>
                                <Style TargetType="ComboBox">
                                    <Setter Property="ItemsSource" Value="{Binding Path=Signals}" />
                                </Style>
                            </toolkit:DataGridComboBoxColumn.ElementStyle>
                            <toolkit:DataGridComboBoxColumn.EditingElementStyle>
                                <Style TargetType="ComboBox">
                                    <Setter Property="ItemsSource" Value="{Binding Path=Signals}" />
                                </Style>
                            </toolkit:DataGridComboBoxColumn.EditingElementStyle>
                        </toolkit:DataGridComboBoxColumn>