Question

A problem arise during orientation change for my app. The app is simple, with just a grid (“contentpanel”)
with a margin and a nested grid called “wrapper”, with constant 20px margin.

The width of the wrapper should be 728px - 20px *2 = 688.

However, when I switch to Portrait orientation, and then back to Landscape orientation,
althought nothing is changed, the width is now 728px.

Image: http://imageshack.us/photo/my-images/713/15445549.jpg

XAML:

<phone:PhoneApplicationPage
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
    xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    x:Class="ManipulationPhoto.TestPhoto2"
    FontFamily="{StaticResource PhoneFontFamilyNormal}"
    FontSize="{StaticResource PhoneFontSizeNormal}"
    Foreground="{StaticResource PhoneForegroundBrush}"
    SupportedOrientations="PortraitOrLandscape"  Orientation="Portrait"
    mc:Ignorable="d" d:DesignHeight="768" d:DesignWidth="480"
    shell:SystemTray.IsVisible="True">

    <Grid x:Name="LayoutRoot" Background="Transparent">
        <Grid.RowDefinitions>
            <RowDefinition Height="176"/>
            <RowDefinition Height="592*"/>
        </Grid.RowDefinitions>
        <StackPanel  x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">
            <TextBlock x:Name="uiDebug" Text="APPLICAZIONE" Style="{StaticResource PhoneTextNormalStyle}"/>
            <Button Content="Button" Height="71" Name="button1" Width="160" Click="button1_Click" />
        </StackPanel>
        <Grid Background="AliceBlue" x:Name="ContentPanel" Grid.Row="1" Margin="0,0,0,0">
            <Grid Name="uiWrapper" Background="Brown"  Margin="20,20,20,20">
            </Grid>
        </Grid>
    </Grid>
</phone:PhoneApplicationPage>

C#

public TestPhoto2()
{
    InitializeComponent();
    this.OrientationChanged += new EventHandler<OrientationChangedEventArgs>(TestPhoto2_OrientationChanged);
}

void TestPhoto2_OrientationChanged(object sender, OrientationChangedEventArgs e)
{
    uiDebug.Text = "h:" + uiWrapper.RenderSize.Height + " l: " + uiWrapper.RenderSize.Width;
}

Answer 1

In your event handler your controls is not resized yet. You receive OLD sizes. With Dispatcher all works well for me:

Dispatcher.BeginInvoke(() =>
{
    uiDebug.Text = "h:" + uiWrapper.RenderSize.Height + " l: " + uiWrapper.RenderSize.Width;
});