Ribbon and Cancas

Hi!

I have a lot WPF Mask in Canvas not Grid!

And on this masks i will build in Ribbons but i found no sample how i can do that with canvas...

To the Background:

In Grid i can  strech the window and the ribbons bill strecht too...

On Canvas that will not work...

Here is a smal xaml code sample:

<ribbon:RibbonWindow x:Class="RibbonApplication.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:ribbon="clr-namespace:Microsoft.Windows.Controls.Ribbon;assembly=RibbonControlsLibrary"
        Title="MainWindow"
		x:Name="RibbonWindow"
		Width="640" Height="480"><Canvas x:Name="LayoutRoot"><ribbon:Ribbon x:Name="_ribbon"><ribbon:Ribbon.ApplicationMenu><ribbon:RibbonApplicationMenu SmallImageSource="Images\SmallIcon.png"><ribbon:RibbonApplicationMenuItem Header="Hello _Ribbon"
                                                      x:Name="MenuItem1"
                                                      ImageSource="Images\LargeIcon.png"/></ribbon:RibbonApplicationMenu></ribbon:Ribbon.ApplicationMenu><ribbon:Ribbon.QuickAccessToolBar><ribbon:RibbonQuickAccessToolBar><ribbon:RibbonButton
                        SmallImageSource="Images\accessories_dictionary.png" 
                        x:Name="_save"/><ribbon:RibbonButton
                        SmallImageSource="Images\aqua_smooth_folder_documents.png"
                        x:Name="_back" /></ribbon:RibbonQuickAccessToolBar></ribbon:Ribbon.QuickAccessToolBar><ribbon:RibbonTab x:Name="HomeTab" 
                              Header="Home"><ribbon:RibbonGroup x:Name="Group1" 
                                    Header="Group1"><ribbon:RibbonButton x:Name="Button1"
                                         LargeImageSource="Images\LargeIcon.png"
                                         Label="Button1" /><ribbon:RibbonButton x:Name="Button2"
                                         SmallImageSource="Images\SmallIcon.png"
                                         Label="Button2" /><ribbon:RibbonButton x:Name="Button3"
                                         SmallImageSource="Images\SmallIcon.png"
                                         Label="Button3" /><ribbon:RibbonButton x:Name="Button4"
                                         SmallImageSource="Images\SmallIcon.png"
                                         Label="Button4" /></ribbon:RibbonGroup></ribbon:RibbonTab></ribbon:Ribbon><Label Canvas.Left="104" Canvas.Top="186" Content="Label" Height="28" Name="label1" /><Button Canvas.Left="279" Canvas.Top="187" Content="Button" Height="23" Name="button5" Width="75" /><TextBox Canvas.Left="148" Canvas.Top="186" Height="23" Name="textBox1" Width="120" /></Canvas></ribbon:RibbonWindow>

What must i cahnge that the ribbon will strech too?

Best regards

Bernd