CheckComboBox : How to prevent a combobox from closing after a selection is clicked?

Question

I\'ve got a combobox and it\'s populated with a bunch of checkboxes. I wish the user to be able to click multiple times before the combobox closes (or is closed by the user

Answer 1

Using Exapander Control you can achieve multple item selection without closing popup after single selection.

For understanding please run this code separately.

xaml

  <Window.Resources>
    <ControlTemplate x:Key="ComboboxToggleButton" TargetType="{x:Type ToggleButton}">
        <Grid Background="{Binding Background,RelativeSource={RelativeSource AncestorType={x:Type ComboBox}}}">
            <Grid.ColumnDefinitions>
                <ColumnDefinition />
                <ColumnDefinition Width="35" />
            </Grid.ColumnDefinitions>
            <Border x:Name="Border" Grid.ColumnSpan="2" Background="Transparent"  BorderBrush="Black" BorderThickness="{Binding BorderThickness,RelativeSource={RelativeSource TemplatedParent}}"/>
            <Path x:Name="Arrow" Grid.Column="1" Opacity="1" Stroke="Black" StrokeThickness="1.5" HorizontalAlignment="Center" VerticalAlignment="Center" Data="M 0 0 L 6 6 L 12 0" />
            <Path x:Name="Arrow_checked" Opacity="0" Grid.Column="1" Fill="Black" Stroke="Black" StrokeThickness="1" HorizontalAlignment="Center" VerticalAlignment="Center" Data="M 0 0 L 6 6 L 12 0 Z" />
            <ContentPresenter TextElement.FontFamily="Segoe Ui Dark" TextElement.FontSize="18" TextElement.Foreground="Black" VerticalAlignment="Center"  Grid.Column="0" Margin="10,0,0,0" HorizontalAlignment="Left" RecognizesAccessKey="True" SnapsToDevicePixels="True" />
        </Grid>
        <ControlTemplate.Triggers>
            <Trigger Property="ToggleButton.IsMouseOver" Value="true">
                <Setter TargetName="Border" Property="Background" Value="Gray" />
                <Setter TargetName="Border" Property="BorderThickness" Value="1.2" />
            </Trigger>
            <Trigger Property="IsChecked" Value="False">
                <Setter Property="Opacity" Value="1" TargetName="Arrow"/>
                <Setter Property="Opacity" Value="0" TargetName="Arrow_checked"/>
            </Trigger>
            <Trigger Property="ToggleButton.IsChecked" Value="true">
                <Setter Property="Opacity" Value="0" TargetName="Arrow"/>
                <Setter Property="Opacity" Value="1" TargetName="Arrow_checked"/>
            </Trigger>
            <Trigger Property="IsEnabled" Value="False">
                <Setter TargetName="Border" Property="Background" Value="Gray" />
                <Setter TargetName="Border" Property="BorderBrush" Value="White" />
            </Trigger>
        </ControlTemplate.Triggers>
    </ControlTemplate>

    <Style TargetType="{x:Type Expander}">
        <Setter Property="FontFamily" Value="Segoe Ui Dark"></Setter>
        <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
        <Setter Property="VerticalContentAlignment" Value="Stretch"/>
        <Setter Property="MaxHeight" Value="200"></Setter>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Expander}">
                    <DockPanel>
                        <ToggleButton x:Name="HeaderSite" Height="35" Background="{TemplateBinding Background}" ContentTemplate="{TemplateBinding HeaderTemplate}" ContentTemplateSelector="{TemplateBinding HeaderTemplateSelector}" Content="{TemplateBinding Header}" DockPanel.Dock="Top" Foreground="Black"   FontStyle="{TemplateBinding FontStyle}"   FontFamily="Segoe UI Dark" 
                     IsChecked="{Binding IsExpanded, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"   Template="{StaticResource ComboboxToggleButton}" />
                        <Border  BorderThickness="0,4.5,0,0" BorderBrush="Transparent">
                            <Border x:Name="bod" BorderBrush="Transparent" SnapsToDevicePixels="True" BorderThickness="1">
                                <ContentPresenter x:Name="ExpandSite"  Focusable="false" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"  Visibility="Collapsed" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
                            </Border>
                        </Border>
                    </DockPanel>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsExpanded" Value="true">
                            <Setter Property="Visibility" TargetName="ExpandSite" Value="Visible"/>
                            <Setter Property="BorderBrush" TargetName="bod" Value="Black"/>
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Foreground" Value="Gray"></Setter>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style x:Key="itemstyle"   TargetType="{x:Type ListBoxItem}">
        <Setter Property="SnapsToDevicePixels" Value="true" />
        <Setter Property="OverridesDefaultStyle"  Value="true" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ListBoxItem">
                    <Grid x:Name="Border"  Height="40"  SnapsToDevicePixels="true">
                        <Grid.Background>
                            <SolidColorBrush Color="Transparent" />
                        </Grid.Background>
                        <ContentPresenter Name="cmb_name" TextElement.FontFamily="Segoe Ui Dark" TextElement.FontSize="18" TextElement.Foreground="Black" Margin="10,0,0,0" VerticalAlignment="Center"></ContentPresenter>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter TargetName="Border" Property="Background" Value="Gray"></Setter>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Setter Property="FocusVisualStyle">
            <Setter.Value>
                <Style TargetType="Control">
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate>
                                <Border BorderBrush="{DynamicResource customBlueBrush}" BorderThickness="1" Margin="1,2,2,2" >
                                    <Rectangle Fill="{DynamicResource customBlueBrush}" Opacity="0.1"></Rectangle>
                                </Border>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </Setter.Value>
        </Setter>
    </Style>

    <Style  TargetType="CheckBox" >
        <Setter Property="SnapsToDevicePixels" Value="True"></Setter>
        <Setter Property="OverridesDefaultStyle" Value="True"></Setter>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="CheckBox">
                    <Grid x:Name="ab" Background="Transparent">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="30"/>
                            <ColumnDefinition/>
                        </Grid.ColumnDefinitions>
                        <Rectangle VerticalAlignment="Center" Height="20" Width="20"  Fill="White" HorizontalAlignment="Left"></Rectangle>
                        <Grid x:Name="checkGrid" VerticalAlignment="Center" Height="20" Width="20" Background="Black" HorizontalAlignment="Left">
                            <Viewbox Height="13" Width="13">
                                <Path x:Name="Check" SnapsToDevicePixels="True" UseLayoutRounding="True" Width="18.7969" Height="16.3094" Canvas.Left="0" Canvas.Top="1.52588e-005" Stretch="Fill" Fill="White" Data="F1 M 0.731262,8.75935L 0.106262,8.08437C 0.0354614,7.9948 0,7.8979 0,7.79375C 0,7.66875 0.0479736,7.5573 0.143799,7.45937L 1.94067,5.77187C 2.02606,5.69893 2.12708,5.66249 2.24377,5.66249C 2.30212,5.66249 2.36096,5.67397 2.42035,5.69685C 2.47974,5.71977 2.52814,5.75417 2.56567,5.79997L 7.5188,11.1406L 16.0438,0.165604C 16.1417,0.055191 16.2584,1.52588e-005 16.3938,1.52588e-005C 16.4979,1.52588e-005 16.5896,0.0322723 16.6688,0.0968475L 18.6313,1.60939C 18.6709,1.64272 18.7084,1.69011 18.7438,1.75154C 18.7792,1.813 18.7969,1.8698 18.7969,1.92189C 18.7969,2.03435 18.7646,2.1385 18.7,2.23439L 7.74377,16.3094L 0.731262,8.75935 Z " />
                            </Viewbox>
                        </Grid>
                        <Grid Background="Transparent" Grid.Column="1" IsHitTestVisible="True" HorizontalAlignment="Stretch">
                            <TextBlock VerticalAlignment="Center"  FontSize="18" FontFamily="Segoe Ui Dark" Foreground="Black"  TextTrimming="CharacterEllipsis">
                        <ContentPresenter></ContentPresenter>
                            </TextBlock>
                        </Grid>

                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="True">
                            <Setter Property="Opacity" Value="1"  TargetName="Check"></Setter>
                        </Trigger>
                        <Trigger Property="IsChecked" Value="False">
                            <Setter Property="Opacity" Value="0" TargetName="Check"></Setter>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Setter Property="FocusVisualStyle">
            <Setter.Value>
                <Style TargetType="Control">
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate>
                                <Border BorderBrush="{DynamicResource customBlueBrush}" SnapsToDevicePixels="True" BorderThickness="1" Margin="-5,1,3,1" />
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>

<Grid x:Name="gd" >
    <Expander Width="500">
        <Expander.Header>
            <ListBox Background="Transparent" IsHitTestVisible="False" BorderBrush="Transparent" ScrollViewer.HorizontalScrollBarVisibility="Hidden" ScrollViewer.VerticalScrollBarVisibility="Disabled"  BorderThickness="0" ItemsSource="{Binding ElementName=lst,Path=SelectedItems}">
                <ListBox.ItemsPanel>
                    <ItemsPanelTemplate>
                        <WrapPanel  Orientation="Horizontal"></WrapPanel>
                    </ItemsPanelTemplate>
                </ListBox.ItemsPanel>
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding ContentData}"/>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
        </Expander.Header>
        <Expander.Content>
            <ListBox  Background="Transparent" ItemContainerStyle="{StaticResource itemstyle}" HorizontalContentAlignment="Stretch" x:Name="lst" SelectionMode="Multiple">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <CheckBox x:Name="checkBox"  IsChecked="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListBoxItem}}, Path=IsSelected}" Content="{Binding ContentData}"></CheckBox>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
        </Expander.Content>
    </Expander>
</Grid>

c# code

  public partial class Window1 : Window
{
    public Window1()
    {
        InitializeComponent();          
        ObservableCollection<Customer> custdata = new ObservableCollection<Customer>();
        custdata.Add(new Customer() { ContentData = "content1" });
        custdata.Add(new Customer() { ContentData = "content2" });
        custdata.Add(new Customer() { ContentData = "content3" });
        custdata.Add(new Customer() { ContentData = "content4" });
        custdata.Add(new Customer() { ContentData = "content5" });
        custdata.Add(new Customer() { ContentData = "content6" });
        lst.ItemsSource = custdata;
    }
}
public class Customer
{
    public string ContentData { get; set; }
}

Result

Answer 2

Konrad,

I also decided to use a ComboBox in this manner, because the code was just dead simple. The easiest way I have found to keep the ComboBox popup open is to wire-up to the PreviewMouseDown event of the control in the ComboBox's item template. handle the behavior yourself, and then mark the mouse event handled. Works great for me. In the sample below, each object in FilterItems is a simple view model with a Text property and an IsChecked property.

<ComboBox IsEditable="True" IsReadOnly="False" ItemsSource="{Binding FilterItems}">
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <CheckBox IsChecked="{Binding IsChecked}" Content="{Binding Text}" 
                      PreviewMouseDown="FilterComboBox_PreviewMouseDown"/>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

And then my event handler is:

private void FilterComboBox_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
    var cb = sender as CheckBox;
    if (cb != null)
    {
        cb.IsChecked = !cb.IsChecked;
        e.Handled = true;
    }
}