WPF(Grid与布局）

<Window x:Class="TestOfGrid.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">    <Grid x:Name="gridMain">        <Grid.ColumnDefinitions >            <ColumnDefinition />            <ColumnDefinition />            <ColumnDefinition />        </Grid.ColumnDefinitions>                <Grid.RowDefinitions >            <RowDefinition Height="30px"/>            <RowDefinition Height="30"/>            <RowDefinition Height="0.5in"/>            <RowDefinition Height="1cm"/>            <RowDefinition Height="30pt"/>        </Grid.RowDefinitions>    </Grid></Window>