将垂直拆分器更改为

<GridSplitter Grid.Column="0" Width="5" ResizeDirection="Auto" 
            Grid.RowSpan="1" 
            HorizontalAlignment="Right" 
            VerticalAlignment="Stretch"/>

这将是使用GridSplitter的更好方法

This will be much better way to use GridSplitter

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="5"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>

    <StackPanel Background="Aqua" Grid.Column="0" >
        <TextBlock FontSize="35" Foreground="#58290A" 
           TextWrapping="Wrap">Left Hand Side</TextBlock>


    </StackPanel>

    <GridSplitter Grid.Column="1" HorizontalAlignment="Stretch"/>

    <Grid Grid.Column="2">
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="5" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <ListBox Grid.Row="0" Background="Red">
            <ListBoxItem>Hello</ListBoxItem>
            <ListBoxItem>World</ListBoxItem>
        </ListBox>
        <GridSplitter Grid.Row="1" Background="Gray" HorizontalAlignment="Stretch"/>
        <ListBox Grid.Row="2" Background="Violet">
            <ListBoxItem>Hello</ListBoxItem>
            <ListBoxItem>World</ListBoxItem>
        </ListBox>
    </Grid>
</Grid>