Host WPF EXE into WPF project

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C#

WPF

Hello guys,
I'm using a WindowsFormsHost to hosting an external EXE into my WPF application.
If I host a WinForm application this working good.
The problem begin when I try to host a WPF EXE application. The application is loaded, but is visualized only the external border, with a transparent on black content.
The other part of the application is loaded only when I click on the upper border.

I'm going crazy...

Thanks all those who can help me..

Here the code.

WindowsFormsHost wfh = new WindowsFormsHost();
F.Panel panel1 = new F.Panel();

Grid MainGrid = new Grid();
MainGrid.Children.Add(wfh);

TabItem Tab = new TabItem();
Tab.Content = MainGrid;
MyTabContainer.Items.Add(Tab);

ProcessStartInfo psi = new ProcessStartInfo(@"c:\app\myWPFapp.exe");
Process p = Process.Start(psi);

for (int i = 0; i < 1000; i++)
         {
           System.Threading.Thread.Sleep(10);
           p.Refresh();
           if (p.MainWindowHandle != IntPtr.Zero)
            {
             break;
            }
         }

SetParent(p.MainWindowHandle, panel1.Handle);
ShowWindow(p.MainWindowHandle, SW_SHOWMAXIMIZED);

Tab.Focus();

Davide