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Esempio di ControlTemplate del controllo ComboBox

Aggiornamento: novembre 2007

I controlli disponibili in Windows Presentation Foundation (WPF) includono un oggetto ControlTemplate che contiene la relativa struttura ad albero visuale. È possibile modificare la struttura e l'aspetto di un controllo modificando il relativo oggetto ControlTemplate. Non è possibile sostituire solo una parte della struttura ad albero visuale di un controllo. Per modificare la struttura ad albero visuale di un controllo, è necessario impostare la proprietà Template di tale controllo sul relativo oggetto ControlTemplate nuovo e completo.

In questo argomento viene illustrato l'oggetto ControlTemplate del controllo ComboBox di WPF.

Nel presente argomento sono contenute le seguenti sezioni.

Per eseguire gli esempi di questo argomento, è necessario disporre di conoscenze su come scrivere applicazioni WPF. Per ulteriori informazioni, vedere Guida introduttiva a Windows Presentation Foundation. È inoltre necessario comprendere l'utilizzo degli stili in WPF. Per ulteriori informazioni, vedere Applicazione di stili e modelli.

Anche se questo esempio contiene tutti gli elementi definiti nell'oggetto ControlTemplate di un controllo ComboBox per impostazione predefinita, i valori specifici devono essere considerati come esempi.

<ControlTemplate x:Key="ComboBoxToggleButton" TargetType="ToggleButton">
  <Grid>
    <Grid.ColumnDefinitions>
      <ColumnDefinition />
      <ColumnDefinition Width="20" />
    </Grid.ColumnDefinitions>
    <Border
      x:Name="Border" 
      Grid.ColumnSpan="2"
      CornerRadius="2"
      Background="{StaticResource NormalBrush}"
      BorderBrush="{StaticResource NormalBorderBrush}"
      BorderThickness="1" />
    <Border 
      Grid.Column="0"
      CornerRadius="2,0,0,2" 
      Margin="1" 
      Background="{StaticResource WindowBackgroundBrush}" 
      BorderBrush="{StaticResource NormalBorderBrush}"
      BorderThickness="0,0,1,0" />
    <Path 
      x:Name="Arrow"
      Grid.Column="1"     
      Fill="{StaticResource GlyphBrush}"
      HorizontalAlignment="Center"
      VerticalAlignment="Center"
      Data="M 0 0 L 4 4 L 8 0 Z"/>
  </Grid>
  <ControlTemplate.Triggers>
    <Trigger Property="ToggleButton.IsMouseOver" Value="true">
      <Setter TargetName="Border" Property="Background" Value="{StaticResource DarkBrush}" />
    </Trigger>
    <Trigger Property="ToggleButton.IsChecked" Value="true">
      <Setter TargetName="Border" Property="Background" Value="{StaticResource PressedBrush}" />
    </Trigger>
    <Trigger Property="IsEnabled" Value="False">
      <Setter TargetName="Border" Property="Background" Value="{StaticResource DisabledBackgroundBrush}" />
      <Setter TargetName="Border" Property="BorderBrush" Value="{StaticResource DisabledBorderBrush}" />
      <Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}"/>
      <Setter TargetName="Arrow" Property="Fill" Value="{StaticResource DisabledForegroundBrush}" />
    </Trigger>
  </ControlTemplate.Triggers>
</ControlTemplate>

<ControlTemplate x:Key="ComboBoxTextBox" TargetType="TextBox">
  <Border x:Name="PART_ContentHost" Focusable="False" Background="{TemplateBinding Background}" />
</ControlTemplate>

<Style x:Key="{x:Type ComboBox}" TargetType="ComboBox">
  <Setter Property="SnapsToDevicePixels" Value="true"/>
  <Setter Property="OverridesDefaultStyle" Value="true"/>
  <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
  <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
  <Setter Property="ScrollViewer.CanContentScroll" Value="true"/>
  <Setter Property="MinWidth" Value="120"/>
  <Setter Property="MinHeight" Value="20"/>
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="ComboBox">
        <Grid>
          <ToggleButton 
            Name="ToggleButton" 
            Template="{StaticResource ComboBoxToggleButton}" 
            Grid.Column="2" 
            Focusable="false"
            IsChecked="{Binding Path=IsDropDownOpen,Mode=TwoWay,RelativeSource={RelativeSource TemplatedParent}}"
            ClickMode="Press">
          </ToggleButton>
          <ContentPresenter
            Name="ContentSite"
            IsHitTestVisible="False" 
            Content="{TemplateBinding SelectionBoxItem}"
            ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}"
            ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"
            Margin="3,3,23,3"
            VerticalAlignment="Center"
            HorizontalAlignment="Left" />
          <TextBox x:Name="PART_EditableTextBox"
            Style="{x:Null}" 
            Template="{StaticResource ComboBoxTextBox}" 
            HorizontalAlignment="Left" 
            VerticalAlignment="Center" 
            Margin="3,3,23,3"
            Focusable="True" 
            Background="Transparent"
            Visibility="Hidden"
            IsReadOnly="{TemplateBinding IsReadOnly}"/>
          <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 WindowBackgroundBrush}"
                BorderThickness="1"
                BorderBrush="{StaticResource SolidBorderBrush}"/>
              <ScrollViewer Margin="4,6,4,6" SnapsToDevicePixels="True">
                <StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Contained" />
              </ScrollViewer>
            </Grid>
          </Popup>
        </Grid>
        <ControlTemplate.Triggers>
          <Trigger Property="HasItems" Value="false">
            <Setter TargetName="DropDownBorder" Property="MinHeight" Value="95"/>
          </Trigger>
          <Trigger Property="IsEnabled" Value="false">
            <Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}"/>
          </Trigger>
          <Trigger Property="IsGrouping" Value="true">
            <Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
          </Trigger>
          <Trigger SourceName="Popup" Property="Popup.AllowsTransparency" Value="true">
            <Setter TargetName="DropDownBorder" Property="CornerRadius" Value="4"/>
            <Setter TargetName="DropDownBorder" Property="Margin" Value="0,2,0,0"/>
          </Trigger>
          <Trigger Property="IsEditable"
               Value="true">
            <Setter Property="IsTabStop" Value="false"/>
            <Setter TargetName="PART_EditableTextBox" Property="Visibility"	Value="Visible"/>
            <Setter TargetName="ContentSite" Property="Visibility" Value="Hidden"/>
          </Trigger>
        </ControlTemplate.Triggers>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
  <Style.Triggers>
  </Style.Triggers>
</Style>


Nell'esempio precedente vengono utilizzate una o più delle risorse seguenti.

<!-- Fill Brushes -->

<LinearGradientBrush x:Key="NormalBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#FFF" Offset="0.0"/>
      <GradientStop Color="#CCC" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="HorizontalNormalBrush" StartPoint="0,0" EndPoint="1,0">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#FFF" Offset="0.0"/>
      <GradientStop Color="#CCC" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="LightBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#FFF" Offset="0.0"/>
      <GradientStop Color="#EEE" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="HorizontalLightBrush" StartPoint="0,0" EndPoint="1,0">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#FFF" Offset="0.0"/>
      <GradientStop Color="#EEE" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="DarkBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#FFF" Offset="0.0"/>
      <GradientStop Color="#AAA" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="PressedBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#BBB" Offset="0.0"/>
      <GradientStop Color="#EEE" Offset="0.1"/>
      <GradientStop Color="#EEE" Offset="0.9"/>
      <GradientStop Color="#FFF" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<SolidColorBrush x:Key="DisabledForegroundBrush" Color="#888" />

<SolidColorBrush x:Key="DisabledBackgroundBrush" Color="#EEE" />

<SolidColorBrush x:Key="WindowBackgroundBrush" Color="#FFF" />

<SolidColorBrush x:Key="SelectedBackgroundBrush" Color="#DDD" />

<!-- Border Brushes -->

<LinearGradientBrush x:Key="NormalBorderBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#CCC" Offset="0.0"/>
      <GradientStop Color="#444" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="HorizontalNormalBorderBrush" StartPoint="0,0" EndPoint="1,0">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#CCC" Offset="0.0"/>
      <GradientStop Color="#444" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="DefaultedBorderBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#777" Offset="0.0"/>
      <GradientStop Color="#000" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<LinearGradientBrush x:Key="PressedBorderBrush" StartPoint="0,0" EndPoint="0,1">
  <GradientBrush.GradientStops>
    <GradientStopCollection>
      <GradientStop Color="#444" Offset="0.0"/>
      <GradientStop Color="#888" Offset="1.0"/>
    </GradientStopCollection>
  </GradientBrush.GradientStops>
</LinearGradientBrush>

<SolidColorBrush x:Key="DisabledBorderBrush" Color="#AAA" />

<SolidColorBrush x:Key="SolidBorderBrush" Color="#888" />

<SolidColorBrush x:Key="LightBorderBrush" Color="#AAA" />

<!-- Miscellaneous Brushes -->
<SolidColorBrush x:Key="GlyphBrush" Color="#444" />

<SolidColorBrush x:Key="LightColorBrush" Color="#DDD" />



Per l'esempio completo, vedere Esempio di applicazione di stili con ControlTemplate.

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