Unable to run my own created exe inside parrent form (vb.net) - vb.net

Question

I have been able to run an external program using the following code.
Imports System.Runtime.InteropServices
Public Class Form1
<DllImport("user32.dll")> Public Shared Function SetParent(ByVal hwndChild As IntPtr, ByVal hwndNewParent As IntPtr) As Integer
End Function
Private Sub Button1_Click_1(sender As Object, e As EventArgs) Handles Button1.Click
Dim PRO As Process = New Process
PRO.StartInfo.FileName = ("notepad.exe")
PRO.Start()
Do Until PRO.WaitForInputIdle = True
'Nothing
Loop
SetParent(PRO.MainWindowHandle, Me.Handle)
PRO.Dispose()
End Sub
This works fine..... (for notepad that is)
However If I swich notepad for my own vb.net application it fails to launch that aplication inside the form but rather runs it outside of the form. I thought that the application I am trying to launch might of had somthing in it so I created a new application with nothing in it (as bare as I could get it) and run that instead of notepad but it also fails to launch within its "parent" form but rather it also triggers outside of the "parent" form insted?
Could someone please help me fix this?

Answer 1

You just need to wait a tiny bit longer for the MainWindowHandle property to be populated.
Here's a kludge that'll do it:
Private Async Sub Button1_Click_1(sender As Object, e As EventArgs) Handles Button1.Click
Dim PRO As Process = New Process
PRO.StartInfo.FileName = ("C:\Users\mikes\Desktop\temp.exe")
PRO.Start()
Await Task.Run(Sub()
PRO.WaitForInputIdle()
While PRO.MainWindowHandle.Equals(IntPtr.Zero)
Threading.Thread.Sleep(10)
End While
End Sub)
SetParent(PRO.MainWindowHandle, Me.Handle)
End Sub
If you want a ten second fail-safe, and exceptions caught, then you could change it up to:
Private Async Sub Button1_Click_1(sender As Object, e As EventArgs) Handles Button1.Click
Try
Dim PRO As Process = New Process
PRO.StartInfo.FileName = ("C:\Users\mikes\Desktop\temp.exe")
PRO.Start()
Await Task.Run(Sub()
Dim timeout As DateTime = DateTime.Now.AddSeconds(10)
While timeout > DateTime.Now AndAlso PRO.MainWindowHandle.Equals(IntPtr.Zero)
Threading.Thread.Sleep(10)
End While
End Sub)
If (Not PRO.MainWindowHandle.Equals(IntPtr.Zero)) Then
SetParent(PRO.MainWindowHandle, Me.Handle)
Else
MessageBox.Show("Timed out waiting for main window handle.", "Failed to Launch External Application")
End If
Catch ex As Exception
MessageBox.Show(ex.ToString, "Failed to Launch External Application")
End Try
End Sub