<Setter Property="BorderBrush" Value="{x:Null}" />在WPF中起什么作用

在WPF（Windows Presentation Foundation）中，<Setter Property="BorderBrush" Value="{x:Null}" /> 的作用是将指定元素的 BorderBrush 属性设置为 null（空），从而移除元素的边框颜色。通常情况下，BorderBrush 属性用于定义元素的边框颜色，而将其设置为 null 可以使元素没有边框。

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WPF Datepicker样式

WPF 的 DatePicker 控件的样式可以通过自定义控件模板来实现，以下是一些示例代码：

1. 在XAML文件中定义DatePicker的控件模板：

<Style TargetType="DatePicker">
    <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.WindowTextBrushKey}}" />
    <Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.WindowBrushKey}}" />
    <Setter Property="BorderBrush" Value="{DynamicResource {x:Static SystemColors.InactiveBorderBrushKey}}" />
    <Setter Property="BorderThickness" Value="1" />
    <Setter Property="Padding" Value="2,0,0,0" />
    <Setter Property="HorizontalAlignment" Value="Left" />
    <Setter Property="VerticalAlignment" Value="Top" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="DatePicker">
                <Grid>
                    <Grid.Resources>
                        <SolidColorBrush x:Key="DisabledBrush" Color="#A5FFFFFF" />
                        <ControlTemplate x:Key="DropDownButtonTemplate" TargetType="Button">
                            <Grid>
                                <VisualStateManager.VisualStateGroups>
                                    <VisualStateGroup x:Name="CommonStates">
                                        <VisualState x:Name="Normal" />
                                        <VisualState x:Name="MouseOver">
                                            <Storyboard>
                                                <ColorAnimation Duration="0" To="#FF448DCA" Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)" Storyboard.TargetName="arrow" />
                                            </Storyboard>
                                        </VisualState>
                                        <VisualState x:Name="Pressed">
                                            <Storyboard>
                                                <ColorAnimation Duration="0" To="#FF2C628B" Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)" Storyboard.TargetName="arrow" />
                                            </Storyboard>
                                        </VisualState>
                                        <VisualState x:Name="Disabled">
                                            <Storyboard>
                                                <DoubleAnimation Duration="0" To="0.5" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="arrow" />
                                            </Storyboard>
                                        </VisualState>
                                    </VisualStateGroup>
                                </VisualStateManager.VisualStateGroups>
                                <Grid Background="Transparent">
                                    <Grid.ColumnDefinitions>
                                        <ColumnDefinition Width="*" />
                                        <ColumnDefinition Width="Auto" />
                                    </Grid.ColumnDefinitions>
                                    <Border x:Name="Background" Grid.ColumnSpan="2" Background="{TemplateBinding Background}" BorderThickness="{TemplateBinding BorderThickness}" BorderBrush="{TemplateBinding BorderBrush}" CornerRadius="2" />
                                    <Border Grid.Column="0" Margin="1" Background="White" CornerRadius="2,0,0,2" />
                                    <Path x:Name="arrow" Grid.Column="1" Fill="#FF606060" HorizontalAlignment="Center" VerticalAlignment="Center" Data="M 0 0 L 4 4 L 8 0 Z">
                                        <Path.RenderTransform>
                                            <ScaleTransform ScaleX="1" ScaleY="1" />
                                        </Path.RenderTransform>
                                    </Path>
                                    <Popup x:Name="Popup" Placement="Bottom" IsOpen="{TemplateBinding IsDropDownOpen}" AllowsTransparency="True" Focusable="False" PopupAnimation="Slide">
                                        <Grid x:Name="DropDown" SnapsToDevicePixels="True" MinWidth="{TemplateBinding ActualWidth}" MaxHeight="{TemplateBinding MaxDropDownHeight}">
                                            <Border x:Name="DropDownBorder" Background="White" BorderThickness="1" BorderBrush="#FF707070" />
                                            <ScrollViewer>
                                                <StackPanel>
                                                    <DatePicker x:Name="PART_TextBox" Style="{x:Null}" />
                                                </StackPanel>
                                            </ScrollViewer>
                                        </Grid>
                                    </Popup>
                                </Grid>
                            </Grid>
                        </ControlTemplate>
                    </Grid.Resources>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <DatePickerTextBox x:Name="PART_TextBox" Grid.Column="0" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Focusable="False" HorizontalContentAlignment="Stretch" IsReadOnly="True" Padding="{TemplateBinding Padding}" VerticalContentAlignment="Stretch" />
                    <Button Grid.Column="1" Focusable="False" IsEnabled="{TemplateBinding IsDropDownOpen}" Template="{StaticResource DropDownButtonTemplate}" />
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

2. 在使用DatePicker时，直接使用该控件模板即可：

<DatePicker Style="{StaticResource {x:Type DatePicker}}" />

以上是一些示例代码，你可以根据自己的需求自定义DatePicker的样式。

WPF 设置listbox滚动条

1. 在XAML中，可以使用ScrollBarStyle属性来设置ListBox的滚动条样式。

2. 可以使用Style属性为ListBox的滚动条定义一个样式。例如，以下是一个简单的样式，它将滚动条的背景颜色设置为灰色：

<ListBox ScrollViewer.VerticalScrollBarStyle="{StaticResource ScrollBarStyle}">
    <ListBox.Resources>
        <Style TargetType="ScrollBar" x:Key="ScrollBarStyle">
            <Setter Property="Background" Value="Gray"/>
        </Style>
    </ListBox.Resources>
</ListBox>

3. 可以使用VisualStateManager类来定义滚动条的不同状态，例如：正常、拖动、禁用等等。以下是一个示例，其中定义了三种状态：

<ListBox ScrollViewer.VerticalScrollBarStyle="{StaticResource ScrollBarStyle}">
    <ListBox.Resources>
        <Style TargetType="ScrollBar" x:Key="ScrollBarStyle">
            <Setter Property="Background" Value="Gray"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="ScrollBar">
                        <Grid>
                            <VisualStateManager.VisualStateGroups>
                                <VisualStateGroup x:Name="CommonStates">
                                    <VisualState x:Name="Normal"/>
                                    <VisualState x:Name="Disabled">
                                        <Storyboard>
                                            <DoubleAnimation Storyboard.TargetName="PART_Thumb"
                                                             Storyboard.TargetProperty="Opacity"
                                                             To="0.5" Duration="0"/>
                                        </Storyboard>
                                    </VisualState>
                                    <VisualState x:Name="MouseOver">
                                        <Storyboard>
                                            <DoubleAnimation Storyboard.TargetName="PART_Thumb"
                                                             Storyboard.TargetProperty="Opacity"
                                                             To="1" Duration="0"/>
                                        </Storyboard>
                                    </VisualState>
                                </VisualStateGroup>
                            </VisualStateManager.VisualStateGroups>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="*"/>
                                <RowDefinition Height="Auto"/>
                            </Grid.RowDefinitions>
                            <Border Grid.Row="0"
                                    Background="{TemplateBinding Background}"
                                    CornerRadius="2"/>
                            <RepeatButton Grid.Row="0"
                                          Style="{StaticResource ScrollBarButtonStyle}"
                                          Command="{TemplateBinding Track.DecreaseCommand}"
                                          IsEnabled="{TemplateBinding Track.DecreaseButton.IsEnabled}"/>
                            <Track Grid.Row="0" Name="PART_Track">
                                <Track.DecreaseRepeatButton>
                                    <RepeatButton Style="{StaticResource ScrollBarButtonStyle}"
                                                  Command="{TemplateBinding Track.DecreaseCommand}"
                                                  IsEnabled="{TemplateBinding Track.DecreaseButton.IsEnabled}"/>
                                </Track.DecreaseRepeatButton>
                                <Track.Thumb>
                                    <Thumb x:Name="PART_Thumb"
                                           Style="{StaticResource ScrollBarThumbStyle}"/>
                                </Track.Thumb>
                                <Track.IncreaseRepeatButton>
                                    <RepeatButton Style="{StaticResource ScrollBarButtonStyle}"
                                                  Command="{TemplateBinding Track.IncreaseCommand}"
                                                  IsEnabled="{TemplateBinding Track.IncreaseButton.IsEnabled}"/>
                                </Track.IncreaseRepeatButton>
                            </Track>
                            <RepeatButton Grid.Row="1"
                                          Style="{StaticResource ScrollBarButtonStyle}"
                                          Command="{TemplateBinding Track.IncreaseCommand}"
                                          IsEnabled="{TemplateBinding Track.IncreaseButton.IsEnabled}"/>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        <Style TargetType="Thumb" x:Key="ScrollBarThumbStyle">
            <Setter Property="Background" Value="#FF8E8F8F"/>
            <Setter Property="BorderThickness" Value="1"/>
            <Setter Property="BorderBrush" Value="#FFCED2D8"/>
            <Setter Property="Width" Value="8"/>
            <Setter Property="Height" Value="20"/>
            <Setter Property="IsTabStop" Value="False"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Thumb">
                        <Border Background="{TemplateBinding Background}"
                                BorderBrush="{TemplateBinding BorderBrush}"
                                BorderThickness="{TemplateBinding BorderThickness}"/>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        <Style TargetType="RepeatButton" x:Key="ScrollBarButtonStyle">
            <Setter Property="Background" Value="Transparent"/>
            <Setter Property="BorderThickness" Value="1"/>
            <Setter Property="BorderBrush" Value="#FFCED2D8"/>
            <Setter Property="Width" Value="10"/>
            <Setter Property="Height" Value="10"/>
            <Setter Property="IsTabStop" Value="False"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="RepeatButton">
                        <Border Background="{TemplateBinding Background}"
                                BorderBrush="{TemplateBinding BorderBrush}"
                                BorderThickness="{TemplateBinding BorderThickness}"/>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </ListBox.Resources>
</ListBox>

4. 可以使用ScrollViewer类来设置ListBox的滚动行为。例如，以下是一个示例，它启用了水平滚动条和垂直滚动条：

<ListBox ScrollViewer.HorizontalScrollBarVisibility="Auto"
         ScrollViewer.VerticalScrollBarVisibility="Auto">
</ListBox>

5. 可以使用ScrollBar类的各种属性和事件来自定义ListBox的滚动条。例如，以下是一个示例，它定义了一个自定义滚动条，该滚动条使用Thumb.DragStarted事件和Thumb.DragDelta事件来更新ListBox的滚动位置：

<ListBox>
    <ListBox.Resources>
        <Style TargetType="ScrollBar">
            <Setter Property="Background" Value="Gray"/>
            <Setter Property="Width" Value="10"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="ScrollBar">
                        <Grid>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="*"/>
                                <RowDefinition Height="Auto"/>
                            </Grid.RowDefinitions>
                            <Border Grid.Row="0"
                                    Background="{TemplateBinding Background}"
                                    CornerRadius="2"/>
                            <Thumb x:Name="PART_Thumb"
                                   Background="#FF8E8F8F"
                                   BorderThickness="1"
                                   BorderBrush="#FFCED2D8"
                                   Width="8"
                                   Height="20"
                                   IsTabStop="False"
                                   DragStarted="PART_Thumb_DragStarted"
                                   DragDelta="PART_Thumb_DragDelta"/>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </ListBox.Resources>
</ListBox>

private void PART_Thumb_DragStarted(object sender, DragStartedEventArgs e)
{
    var thumb = sender as Thumb;
    var scrollBar = thumb.TemplatedParent as ScrollBar;
    if (scrollBar != null)
    {
        scrollBar.CaptureMouse();
    }
}

private void PART_Thumb_DragDelta(object sender, DragDeltaEventArgs e)
{
    var thumb = sender as Thumb;
    var scrollBar = thumb.TemplatedParent as ScrollBar;
    if (scrollBar != null)
    {
        double newValue = scrollBar.Value - e.VerticalChange;
        if (newValue < scrollBar.Minimum)
        {
            newValue = scrollBar.Minimum;
        }
        else if (newValue > scrollBar.Maximum)
        {
            newValue = scrollBar.Maximum;
        }
        scrollBar.Value = newValue;
    }
}

以上是一些设置WPF ListBox滚动条的方法。可以根据需要进行自定义和修改，以满足具体的需求。