How to make a WPF window behave as dialogwindow when launched through process class

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C#

WPF

MVVM

Hi,

I have a small WPF application, say SubWPF , which initially displays a home window that allows the user to browse a file. I am launching this wpf application on the button click of another application say MainWPF. In short, when I click on "Launch Sub", SubWPF.exe is launched from MainWPF through Process class as given below.

Process p = new Process();
p.StartInfo.FileName = "SubWPF.exe";
       
p.StartInfo.WindowStyle = ProcessWindowStyle.Normal;
p.StartInfo.UseShellExecute = false;
p.StartInfo.Verb = "runas";
p.Start();

The issue is in the background I have the MainWPF window. I need the subwpf to be always on top and prevent the user from clicking background buttons of mainwpf. To be precise, the behaviour of a showdialog() needs to be achieved.

What I have tried:

I have tried using  TopMost=true for subwpf home window, but it didn't achieve the functionality as in my subwpf once the user selects a file in the home window, this window is closed and another window showing the contents of file is displayed. Setting TopMost=true is not allowing me to close the file selection window.