BPASmartClient/WPFDemo/Window1.xaml

<Window
    x:Class="WPFDemo.Window1"
    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:local="clr-namespace:WPFDemo"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="Window1"
    Width="800"
    Height="450"
    mc:Ignorable="d">
    <Grid>
        <Grid.RowDefinitions />
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition Width="10" />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>

        <TextBlock
            Grid.Row="0"
            Grid.Column="0"
            Text="LLLLLLLLLLLLLL" />
        <GridSplitter
            Grid.Row="0"
            Grid.Column="1"
            Width="10"
            HorizontalAlignment="Center"
            VerticalAlignment="Stretch"
            Background="Wheat"
            DragDelta="GridSplitter_DragDelta" />

        <Grid Grid.Row="0" Grid.Column="2">
            <Grid.RowDefinitions>
                <RowDefinition />
                <RowDefinition Height="10" />
                <RowDefinition />
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition />
            </Grid.ColumnDefinitions>

            <TextBlock
                Grid.Row="0"
                Grid.Column="0"
                Text="RRRRRRTTTTTTTT" />
            <GridSplitter
                Grid.Row="1"
                Grid.Column="0"
                Height="10"
                HorizontalAlignment="Stretch"
                Background="Wheat" />
            <TextBlock
                Grid.Row="2"
                Grid.Column="0"
                Text="RRRRRRBBBBBBBB" />

        </Grid>
    </Grid>
</Window>