WPF GridSplitter最好设置HorizontalAlignment和VerticalAlignment，否则不可以左右移动

<Window x:Class="XamlTest.Window5"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window5" Height="300" Width="300">
    <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"/>

        <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>