>I think the problem is probably in the c# constructor code for Page1 but it's not possible to say where since you don't show code for WindowsFormsHost or mainForm (if you chop out all of the constructor code except InitializeComponent it compiles OK)
>Regards,
>Viv

WindowsFormsHost is a WPF class, you need to include WindowsFormsIntegration.dll once I did that and gave the application full trust it ran fine.