How to work with Multiple XAML in WPF project

Question

Hi All,
I am testing WPF application for our product. I thought of using different xaml for different scenarios. But as in App.xaml we can only refrence one XAML so i googled it and reach at the following solution:
http://social.msdn.microsoft.com/forums/en-US/wpf/thread/c2484bcb-b321-4cf7-9328-90da7dbbd5d1/   That is:
1st- Remove the tag StartupUri from all the startup xaml's
2nd- Create a method in app.xamls.cs like this:
 
protected override void OnStartup(StartupEventArgs e)
{
this.StartupUri = new System.Uri(file, System.UriKind.Relative);
 }
 
"file" is the name of the xaml that i want to set has starting application. like: window1.xaml or window2.xaml
 
I did the same but it is trowing error:
IOexception was handled "Cannot locate resource 'file'." and if i use direct xaml name
i.e.
this.StartupUri = new System.Uri("Windows1.xaml", System.UriKind.Relative);
then again it is trwing same error:
IOexception was handled "Cannot locate resource Windows1.xaml."
Pleas help 1. How to make use of file in above i mean where i need to define those XAMl so that to refernce with file in :
this.StartupUri = new System.Uri(file, System.UriKind.Relative);
2. When i am directly using XAML name what is the cause of error?
Thanks in advance
looking for you promt reply/suggestion.
Regards
~rakesh