<Window x:Class="WpfApp1.WindowGridDemo"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="WindowGridDemo" Height="300" Width="400">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="61*"/>
            <RowDefinition Height="101*"/>
            <RowDefinition Height="108*"/>
        </Grid.RowDefinitions>
        
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="139"/>
            <ColumnDefinition Width="184*"/>
            <ColumnDefinition Width="45*" />
            <ColumnDefinition Width="250*"/>
        </Grid.ColumnDefinitions>

        <TextBlock   Grid.Row="0" Grid.ColumnSpan="1"  Text="第一行，第一列，占1列" Background="Red" HorizontalAlignment="Center"  />
        <Button Grid.Row="0" Grid.Column="1" Grid.ColumnSpan="3" Grid.RowSpan="2" Content="从第1行第2列开始，占两行，三列" />
        <Button  Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="4" Content="第3行，第1列开始，占4列" />
        <Button Grid.Row="1" Name="btnAddByCode" Click="btnAddByCode_Click" >后台代码生成(第2行第1列)</Button>
    </Grid>
</Window>

即把界面分为3行4列，指定起始位置和占用格数。