Resizable WPF listbox inside Stack Panel?-CodePudding

I'm trying to create a listBox inside a WPF control which (1) has a minimum height of 80 and (2) which the user can resize to larger vertical height, if desired to see more of the list items. I also want the control, when nested inside a vertical stackPanel, to expand in height as the user expands the list. I've been playing around with gridSplitter. My XAML is below:

<UserControl x:Class="MyControl.FieldControl_SelectFrom"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:MyControl"
             mc:Ignorable="d" 
             d:DesignWidth="342">
    <Grid  Background="{x:Static SystemColors.ControlBrush}">
        <Grid.RowDefinitions>
            <RowDefinition Height="*"></RowDefinition>
            <RowDefinition Height="*"></RowDefinition>
            <RowDefinition Height="auto"></RowDefinition>
            <RowDefinition Height="*"></RowDefinition>
        </Grid.RowDefinitions>
        <TextBlock Grid.Row="0" x:Name="textBlock_fieldName" HorizontalAlignment="Left" Margin="20,4,0,0" TextWrapping="Wrap" Text="FieldName" VerticalAlignment="Top" FontWeight="Bold"/>
        <ListBox Grid.Row="1" x:Name="selectorBox" MinHeight="80" Height="auto" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Padding="0,0,0,0"  Margin="20,4,38,4" VerticalContentAlignment="Center" />
        <GridSplitter Grid.Row="2" Height="2" VerticalAlignment="Center"></GridSplitter>
        <TextBlock Grid.Row="3" x:Name="textBlock_fieldInfo" HorizontalAlignment="Left" Margin="20,0,0,6" TextWrapping="Wrap"  VerticalAlignment="Bottom" FontStyle="Italic" Foreground="Gray">Field Info</TextBlock>

    </Grid>
</UserControl>

When I run the project, the listbox is expanded to show the entire contents - with no ability to resize.

What am I missing?

CodePudding user response：

The default resize direction of the GridSplitter is GridResizeDirection.Auto. If you look at the documentation for GridResizeDirection.Auto about the rules that govern behavior of Auto, you'll notice that in your case the GridSplitter -- based on the defined rules as explained in the documentation -- is actually attempting to resize between columns, not rows as you want it to be.

You can make the GridSplitter work in row mode in basically two ways. One is to set the ResizeDirection of the GridSplitter explicitly to GridResizeDirection.Rows. This, however, would not fully solve the problem with the code given in your question.

Because, without specifying the width of the splitter or letting it stretch horizontally (neither of which you have done), the splitter remains a point-like or short vertical line-like element with a width of zero that's practically impossible to hit. So, basically you could tell the splitter to stretch horizontally, which will let the default Auto resize direction operate in Rows mode (and therefore does not require to set the ResizeDirection property explicitly) as well as give the splitter a size that can actually be hit/grabbed with the mouse pointer.