Panel performance

程序：

<StackPanel HorizontalAlignment="Left">
    <StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
        <TextBlock Text="Field 1: " VerticalAlignment="Center"/>
        <TextBox Width="100"/>
    </StackPanel>
    <StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
        <TextBlock Text="Field 2: " VerticalAlignment="Center"/>
        <TextBox Width="100"/>
    </StackPanel>
    <StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
        <TextBlock Text="Longer Field 3: " VerticalAlignment="Center"/>
        <TextBox Width="100"/>
    </StackPanel>
</StackPanel>

有四个StackPanel意味着要执行四次measurement和arrangement,第一个父StackPanel让自己的三个孩子StackPanel执行measurement和arragement,这样性能损失严重，修改为：

Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto"/>
        <ColumnDefinition Width="100"/>
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>

    <TextBlock Text="Field 1: "
               Grid.Column="0"
               Grid.Row="0"
               HorizontalAlignment="Right"
               VerticalAlignment="Center"/>
    <TextBox Grid.Column="1"
             Grid.Row="0"/>

    <TextBlock Text="Field 2: "
               Grid.Column="0"
               Grid.Row="1"
               HorizontalAlignment="Right"
               VerticalAlignment="Center"/>
    <TextBox Grid.Column="1"
             Grid.Row="1"/>

    <TextBlock Text="Longer Field 3: "
               Grid.Column="0"
               Grid.Row="2"
               HorizontalAlignment="Right"
               VerticalAlignment="Center"/>
    <TextBox Grid.Column="1"
             Grid.Row="2"/>
</Grid>

 这样只有一个panel,只需要执行一次measurement 和 arrangement计算。