如何让WPF ListBox内容更新时自动显示滚动条且不改变高度

问题描述 #

我制作了一个可拉伸的WPF窗体，拉伸时ListBox能同步展开查看更多行，但一次性向ListBox添加大量项时，其高度会被内容撑大导致超出屏幕，必须手动拉伸窗体后才会显示滚动条。需要实现以下两个行为：

• 手动拉伸窗体时，ListBox同步拉伸
• 添加项时ListBox高度保持固定，自动显示滚动条

已尝试的方案：

• 将ListBox嵌入DockPanel、Canvas、StackPanel等不同容器
• 使用无容器包裹的ListBox
• 调整ScrollViewer相关设置

核心原因 #

问题根源在于窗体的SizeToContent="WidthAndHeight"属性，该属性会让窗体自动适应所有内容的大小。当ListBox添加大量项时，窗体高度会跟着ListBox一起被撑大，超出屏幕范围，此时ListBox没有被限制高度，自然不会触发滚动条。

解决方案 #

1. 修改窗体的SizeToContent属性 #

将窗体的SizeToContent从WidthAndHeight改为Width，这样窗体宽度仍会自适应内容，但高度由初始设置和用户拉伸控制，不会随ListBox内容自动变大。同时给窗体设置MinHeight，保证初始显示的最小高度。

2. 修正ListBox的布局设置 #

确保ListBox所在的Grid行高度为*（占据剩余空间），并且ListBox的VerticalAlignment="Stretch"，让它填满所在行的空间，同时保留MinHeight防止高度过小。另外修正原代码中重复的Grid.Row="1"属性，添加Grid.ColumnSpan="2"让ListBox横跨两列，和上方布局保持一致。

修改后的完整XAML代码 #

<Window x:Class="B.Revit.BatchUpgrader.Addin.Views.BatchUpgraderWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:B.Revit.BatchUpgrader.Addin.Views"
    mc:Ignorable="d"
    Title="Batch Upgrader 1.0"
    SizeToContent="Width" 
    MinHeight="600" 
    ResizeMode="CanResize"
    WindowStartupLocation="CenterScreen"
    ShowInTaskbar="False"
    Topmost="True">

<Window.Resources>
    <Style TargetType="Button">
        <Setter Property="Height" Value="32"/>
        <Setter Property="Background" Value="White"/>
        <Setter Property="BorderThickness" Value="2"/>
        <Setter Property="BorderBrush" Value="DarkSeaGreen"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="Button">
                    <Border CornerRadius="5" BorderThickness="1" BorderBrush="#FF9DA57F" Background="#FFF4F7E9">
                        <ContentPresenter x:Name="contentPresenter" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="*"/>
        <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*" />
        <ColumnDefinition Width="*" />
    </Grid.ColumnDefinitions>
    <StackPanel Grid.Row="0"
                Grid.ColumnSpan="2"
                Margin="4">

        <GroupBox Header="File Types"
                  Margin="4">
            <StackPanel>
                <CheckBox Content="Project files *.rvt"
                          Margin="4"
                          IsChecked="{Binding IsProjectUpdate}" />
                <CheckBox Content="Family files *.rfa"
                          Margin="4"
                          IsChecked="{Binding IsFamilyUpdate}" />
                <CheckBox Content="Template files *.rte, *.rft"
                          Margin="4"
                          IsChecked="{Binding IsTemplateUpdate}" />
            </StackPanel>
        </GroupBox>

        <GroupBox Header="Saving settings"
                  Margin="4">
            <StackPanel>
                <RadioButton GroupName="SavingSettings"
                             Content="Add a suffix to the file name"
                             Margin="4"
                             IsChecked="{Binding IsAddSuffixSave}" />
                <RadioButton GroupName="SavingSettings" 
                             Content="Save the updated files in a subfolder"
                             Margin="4"
                             IsChecked="{Binding IsSubFolderSave}" />
                <RadioButton GroupName="SavingSettings"
                             Content="Overwrite existing files"
                             Margin="4"
                             IsChecked="{Binding IsOverwriteSave}" />
            </StackPanel>
        </GroupBox>

        <GroupBox Header="Additional settings"
                  Margin="4">
            <StackPanel>
                <CheckBox Content="Delete backup files after update"
                          Margin="4"
                          IsChecked="{Binding IsDeleteBackup}"
                          IsEnabled="{Binding IsDeleteBackupEnable}"/>
                <CheckBox Content="Update families in subfolders"
                          Margin="4"
                          IsChecked="{Binding IsIncludeSubFolders}" />
                <CheckBox Content="Update by ignoring errors"
                          Margin="4"
                          IsChecked="{Binding IsIgnoringErrors}" />
            </StackPanel>
        </GroupBox>

        <Button Content="Select folder with Revit files"
                Height="32"
                Margin="4"
                Command="{Binding SelectFolderButton}">
        </Button>
    </StackPanel>
    <ListBox x:Name="ListFolders"
             Grid.Row="1"
             Grid.ColumnSpan="2"
             MinHeight="80"
             Margin="8 0"
             VerticalAlignment="Stretch"
             ItemsSource="{Binding SelectedDirectories}"
             SelectedItem="{Binding SelectedFolder}"
             MouseDoubleClick="ListBox_MouseDoubleClick"
             KeyDown="ListFolders_KeyDown">
    </ListBox>
    <Button Grid.Row="2"
            Grid.Column="0"
            Content="Upgrade"
            Height="32"
            MinWidth="160"
            Margin="8"
            Command="{Binding RunBatchUpgraderButton}" />
    <Button Grid.Row="2"
            Grid.Column="1"
            Content="Cancel"
            Height="32"
            MinWidth="160"
            Margin="8"
            Command="{Binding CancelBatchUpgraderButton}" />
</Grid>
</Window>

补充说明 #

• 修改SizeToContent="Width"后，窗体高度不会随ListBox内容自动扩展，ListBox被限制在Grid的*行内，当内容超过ListBox高度时会自动显示垂直滚动条。
• VerticalAlignment="Stretch"保证ListBox能随窗体拉伸同步扩大，MinHeight="80"避免ListBox被压缩到过小。

内容的提问来源于stack exchange，提问作者Mikita Yankouski