WPF组合框带有复选框

Question

I am trying to implement a combobox with checkboxes in it. All the articles/resources I found on Google/SO suggest adding a bool to my business object. But I am looking to create a reusable control. So I created a custom control inherited from combobox and changed the control in the popup with a itemscontrol. Here is my XAML (for brevity adding just the xaml for popup)

<Popup Name="Popup" Placement="Bottom" IsOpen="{TemplateBinding IsDropDownOpen}" AllowsTransparency="True" Focusable="False" PopupAnimation="Slide">
 <Grid Name="DropDown" SnapsToDevicePixels="True" MinWidth="{TemplateBinding ActualWidth}"  MaxHeight="{TemplateBinding MaxDropDownHeight}">
  <Border x:Name="DropDownBorder" Background="{StaticResource BackgroundBrush}" BorderThickness="1" BorderBrush="{StaticResource BorderBrush}" />
     <ScrollViewer Margin="4,6,4,6" SnapsToDevicePixels="True">
         <ItemsControl ItemsSource="{Binding ItemsSource,RelativeSource={RelativeSource AncestorType=local:CheckedComboBox}}">
             <ItemsControl.ItemTemplate>
                           <DataTemplate>
                                <CheckBox Content="{Binding}" x:Name="PART_Checkbox" />
                            </DataTemplate>
               </ItemsControl.ItemTemplate>
           </ItemsControl>
     </ScrollViewer>
  </Grid>
</Popup>

As expected it shows a combobox with checkboxes. But I am not able to figure out how to keep track of the checked items? I was thinking of listening to checked events but when I tried getting the Checkbox in my code-behind, FindName was returning null.

public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            if (this.Template != null)
            {
                var v = Template.FindName("PART_Checkbox",this);
                Debug.Assert(v != null);

            }
        }

Thanks.

Answer 1

1. Inherit from ListBox
2. Bind the CheckBox to ListBoxItem.IsSelected in the template of the items (set it in default style via ItemContainerStyle ).
3. Set SelectionMode to Multiple .

SelectedItems then contains your selection. You may also want to bind your selection area to something like a comma-separated list of the SelectedItems (can be done via a converter for example).