Höhe und Breite der viewbox-Steuerelement innerhalb

Ich bin neu in WPF. In meinem code habe ich eine einfache WPF-Fenster mit ein paar Steuerelemente. Die Bedienelemente sind alle in der Ansicht enthaltenen Box. Mein problem ist, dass wenn ich die Größe der Fenster, die Steuerung Größe text ist nicht die Größenänderung proportional. Hier ist mein code:

<Window x:Class="DesktopGoogleReader.UIelements.About"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="About" Height="346" Width="435"
    >
    <Window.Background>
        <LinearGradientBrush StartPoint="0,0" EndPoint="0,0.5">
            <LinearGradientBrush.GradientStops>
                <GradientStop Offset="0" Color="#eee" />
                <GradientStop Offset="1" Color="#ccc" />
            </LinearGradientBrush.GradientStops>
        </LinearGradientBrush>
    </Window.Background>
    <Viewbox Stretch="Uniform">
        <Grid>        
        <Label Height="41" Margin="83,12,12,0" Name="label1" VerticalAlignment="Top" FontSize="20" FontWeight="Bold">Desktop Google Reader</Label>
        <Image Margin="348,0,0,0" Name="image1" Stretch="Fill" Height="65" HorizontalAlignment="Left" VerticalAlignment="Top" Width="65" Source="C:\Users\TRIDIP\Desktop\tmp\Desktop Google Reader WPF good UI\trunk\DesktopGoogleReader\DesktopGoogleReader.ico" />
        <Label Height="28" Margin="92,49,12,0" Name="label_versionName" VerticalAlignment="Top">Version: Versionnumber</Label>
        <TextBlock Margin="12,83,12,0" Name="textBlock1" Height="54" VerticalAlignment="Top" Text="Desktop Google Reader is Windows /.NET based client to the RSS aggregation service Google Reader. It is licensed under the New BSD License (BSD). It is developed by Konstantins Onufrijevs and Sven Walther" TextWrapping="Wrap" />
        <Label Margin="12,134,12,0" Name="label2" Height="29" VerticalAlignment="Top">Credits: Desktop Google Reader uses the following external resources:</Label>
        <Button HorizontalAlignment="Left" Margin="12,161,0,0" Name="button_snarlChsarp" Width="173" Height="23" VerticalAlignment="Top" >Snarl Connector</Button>
        <Button Margin="191,161,0,0" Name="button_TweetSharp" Height="23" VerticalAlignment="Top" HorizontalAlignment="Left" Width="173" >TweetSharp</Button>
        <Button Height="23" HorizontalAlignment="Left" Margin="12,190,0,0" Name="button_iconSet" VerticalAlignment="Top" Width="173" >Function Icon Set</Button>
        <Button Height="23" Margin="191,190,0,0" Name="button_facebook" VerticalAlignment="Top" HorizontalAlignment="Left" Width="173" >Facebook Developer Toolkit</Button>
        <Button Height="23" HorizontalAlignment="Left" Margin="12,219,0,0" Name="button_awesomium" VerticalAlignment="Top" Width="173" >Web Kit .NET</Button>
        <Button Height="23" Margin="191,219,0,0" Name="button_winkle" VerticalAlignment="Top" HorizontalAlignment="Left" Width="173" >Winkle Update System</Button>
        <TextBlock Height="59" Margin="12,248,12,0" Name="textBlock_contributors" VerticalAlignment="Top" Text="Contributors: We want to thank all the people using Desktop Google Reader. A special thanks goes to Henry C. for his continues help in improving and supporting our project." TextAlignment="Left" TextWrapping="Wrap" />
    </Grid>
    </Viewbox>
</Window>