You never need HWND to do this. Remember, using HWND will immediately make your Forms application non-portable. If you write a Forms application accurately, it will run on many platforms without recompilation (under Mono). A single use of HWND will spoil it.
Most importantly, you don't need it.
Instead, you need to create a separate thread and notify UI on progress using a progress bar. Here is how:
You cannot call anything related to UI from non-UI thread. Instead, you need to use the method
Invoke or
BeginInvoke of
System.Windows.Threading.Dispatcher (for both Forms or WPF) or
System.Windows.Forms.Control (Forms only).
You will find detailed explanation of how it works and code samples in my past answers:
Control.Invoke() vs. Control.BeginInvoke()[
^],
Problem with Treeview Scanner And MD5[
^].
See also more references on threading:
How to get a keydown event to operate on a different thread in vb.net[
^],
Control events not firing after enable disable + multithreading[
^].
—SA
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