组合框性能缓慢

Question

正如以下文章 http://vbcity.com/blogs/xtab/archive/2009/12/15/wpf-using-a-virtualizingstackpanel-to-improve-combobox-performance.aspx 所述，我使用VirtualizingStackPanel来提高项目组合框的性能。

而且效果很好...直到我将样式应用于组合框以更改布局（我在这里找到了样式：http://msdn.microsoft.com/en-us/library/ee230084.aspx）

下面是演示此事的示例的源代码（计算ComboBox的ItemSource属性填充了10 000个项目）。

如果有人有想法...

    <Window.Resources>
    <!-- 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="Black" />
    <SolidColorBrush x:Key="DisabledBackgroundBrush" Color="#E5E5E5" />
    <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="#AAA" Offset="0.0"/>
                <GradientStop Color="#AAA" Offset="1.0"/>
            </GradientStopCollection>
        </GradientBrush.GradientStops>
    </LinearGradientBrush>
    <LinearGradientBrush x:Key="HorizontalNormalBorderBrush" StartPoint="0,0" EndPoint="1,0">
        <GradientBrush.GradientStops>
            <GradientStopCollection>
                <GradientStop Color="#AAA" Offset="0.0"/>
                <GradientStop Color="#AAA" Offset="1.0"/>
            </GradientStopCollection>
        </GradientBrush.GradientStops>
    </LinearGradientBrush>
    <LinearGradientBrush x:Key="DefaultedBorderBrush" StartPoint="0,0" EndPoint="0,1">
        <GradientBrush.GradientStops>
            <GradientStopCollection>
                <GradientStop Color="#AAA" Offset="0.0"/>
                <GradientStop Color="#AAA" Offset="1.0"/>
            </GradientStopCollection>
        </GradientBrush.GradientStops>
    </LinearGradientBrush>
    <LinearGradientBrush x:Key="PressedBorderBrush" StartPoint="0,0" EndPoint="0,1">
        <GradientBrush.GradientStops>
            <GradientStopCollection>
                <GradientStop Color="#AAA" Offset="0.0"/>
                <GradientStop Color="#AAA" 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" />
    <ControlTemplate x:Key="ComboBoxToggleButton" TargetType="ToggleButton">
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition />
                <ColumnDefinition Width="16" />
            </Grid.ColumnDefinitions>
            <Border x:Name="Border" Grid.ColumnSpan="2" CornerRadius="2" Background="{StaticResource NormalBrush}" BorderBrush="{StaticResource NormalBorderBrush}" BorderThickness="1" />
            <Border x:Name="Border2" 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 TargetName="Border2" Property="Background" Value="{StaticResource DisabledBackgroundBrush}" />
                <Setter TargetName="Border2" 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="ComboBoxBaseStyle" 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="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>
</Window.Resources>
<StackPanel>
    <ComboBox x:Name="CustomerComboBox_WithoutStyle" SelectedValuePath="Id" DisplayMemberPath="Text" >
        <ComboBox.ItemsPanel>
            <ItemsPanelTemplate>
                <VirtualizingStackPanel />
            </ItemsPanelTemplate>
        </ComboBox.ItemsPanel>
    </ComboBox>
    <ComboBox x:Name="CustomerComboBox_WithStyle" SelectedValuePath="Id" DisplayMemberPath="Text" Style="{StaticResource ComboBoxBaseStyle}" >
        <ComboBox.ItemsPanel>
            <ItemsPanelTemplate>
                <VirtualizingStackPanel />
            </ItemsPanelTemplate>
        </ComboBox.ItemsPanel>
    </ComboBox>
</StackPanel>

Answer 1

您的风格问题在于它不使用任何类型的 UI 虚拟化。尝试将StackPanel替换为VirtualizingStackpanel，并将VirtualizationMode设置为Recycle，您将看到巨大的性能提升。

你的方法强制 WPF 为 10k 项中的每一个实现一个容器和框架元素，这需要很长时间，因为你只有 1 个 UI 线程。只需更换

<StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Contained" />

跟

<VirtualizingStackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Contained" />

看看它是否变得更快。

更准确地说，您可以在派生样式中覆盖 ItemsPanel，但在基本样式中没有"ItemsPresenter"。而是使用StackPanel"硬编码"

Answer 2

如此多的项目可能是（UI）设计缺陷的结果。

尝试使用一个或多个组合框，其中第一个组合框是一个类别，第二个组合框是第一个组合框的子类别。

Answer 3

在一个

组合框中有10000个项目并不是很好的设计。MaxDropDownItems可能会帮助您，因为需要的渲染更少。（这是单击下拉列表时显示的可见项目数）

但是，您应该考虑使用列表框。应用列表框时，应使用页面，并且每个页面上有 1000 条记录。或使用搜索框