[WPF] : ドロップダウン付き TextBox のサンプル

DropDownTextBoxStyle.xaml

<Style x:Key="TextBoxStyle1" TargetType="{x:Type TextBox}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type TextBox}">
                <Border>
                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition />
                            <ColumnDefinition Width="24" />
                        </Grid.ColumnDefinitions>
                        <Microsoft_Windows_Themes:ListBoxChrome 
                            x:Name="Bd" 
                            BorderBrush="{TemplateBinding BorderBrush}" 
                            BorderThickness="{TemplateBinding BorderThickness}" 
                            Background="{TemplateBinding Background}" 
                            RenderMouseOver="{TemplateBinding IsMouseOver}" 
                            RenderFocused="{TemplateBinding IsKeyboardFocusWithin}" 
                            SnapsToDevicePixels="true">
                            <ScrollViewer x:Name="PART_ContentHost" 
                                SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                        </Microsoft_Windows_Themes:ListBoxChrome>
                        <ToggleButton Grid.Column="1" x:Name="ToggleButton1" >

                            <!-- 下矢印 -->
                            <ed:RegularPolygon Height="9" Width="9" 
                                               InnerRadius="90" PointCount="3" Stroke="Gray" 
                                               RenderTransformOrigin="0.5,0.5" Fill="cornflowerblue">
                                <ed:RegularPolygon.RenderTransform>
                                    <TransformGroup>
                                        <RotateTransform Angle="180"/>
                                    </TransformGroup>
                                </ed:RegularPolygon.RenderTransform>
                            </ed:RegularPolygon>

                        </ToggleButton>
                        <Popup x:Name="Popup1" 
                            PlacementTarget="{Binding ElementName=Button1}"
                            PopupAnimation="Fade" Height="Auto" Margin="0,0,0,-46">
                            <TextBox x:Name="PopupText" Width="Auto" Height="Auto"
                                AcceptsReturn="True" TextWrapping="Wrap" IsReadOnly="True"
                                Text="{TemplateBinding Text}" />
                        </Popup>
                    </Grid>
                </Border>

                <ControlTemplate.Triggers>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter Property="Background" TargetName="Bd" 
                                Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
                        <Setter Property="Foreground" 
                                Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                    </Trigger>

                    <!-- ドロップダウン制御 -->
                    <DataTrigger Binding="{Binding IsChecked, ElementName=ToggleButton1}" 
                                    Value="True">
                        <Setter TargetName="Popup1" Property="IsOpen" Value="True" />
                    </DataTrigger>
                    <DataTrigger Binding="{Binding IsFocused, ElementName=PopupText}" Value="True">
                        <Setter TargetName="Popup1" Property="IsOpen" Value="True" />
                    </DataTrigger>
                    <MultiDataTrigger>
                        <MultiDataTrigger.Conditions>
                            <Condition Binding="{Binding IsFocused, ElementName=PopupText}" 
                                        Value="False" />
                            <Condition Binding="{Binding IsFocused, ElementName=ToggleButton1}" 
                                        Value="False" />
                        </MultiDataTrigger.Conditions>
                        <Setter TargetName="ToggleButton1" Property="IsChecked" Value="False" />
                    </MultiDataTrigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>