Frame Page controls layout - wpf

Question

Could you please tell me where I have gone wrong, my frame size takes the size of the wpf window, code is:
<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="BSP" Height="700" Width="990" WindowStartupLocation="CenterScreen">
<Grid Background="Green" VerticalAlignment="Center" HorizontalAlignment="Center" >
<Frame Name="MainFrame" Source="LoginScreen.xaml" NavigationUIVisibility="Hidden" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" />
</Grid>
</Window>
The page size less than the window and also the total size of margin+width+size of label is less than the size of page yet the button is being displayed as cut. Code for the page is below:
<Page x:Class="Loggedin"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
Height="660" Width="920"
Title="Loggedin">
<Grid Background="white" Margin="2">
<StackPanel Orientation="Horizontal" VerticalAlignment="Top" >
<Label Content="Loggedin as" Height="28" HorizontalAlignment="Left" Name="Loggedinas" />
<Button Content="LogOut" Margin="780,0,0,0" Height="28" Name="Logout" Width="50" HorizontalAlignment="Right"/>
</StackPanel>
</Grid>
</Page>
Could you please assist me, it is eating my brain from 2 days :(. Following are pics of output:
Pic from Visual Studios: http://clip2net.com/s/1Fpb7
Pic from Runtime: http://clip2net.com/s/1FpbQ

Answer 1

Have you thought about using a DockPanel instead of a StackPanel? It seems to be a closer fit for the layout you're trying to achieve :
<DockPanel VerticalAlignment="Top">
<Label Content="Loggedin as" Height="28" HorizontalAlignment="Left" Name="Loggedinas" />
<Button Content="LogOut" Height="28" Name="Logout" Width="50" HorizontalAlignment="Right"/>
</DockPanel>
Any time you have margins that look like Margin="780,0,0,0" it usually means you're working too hard and there's a better way to do it. In my quick scratch tests, the 780 pixel left margin was pushing the button off the frame.