Form Disappear Automatically

This is very strange, I have a form, a very simple "Hello World" type of form. If I just do F5, the form shows up, no problem. Now I added a module, with the following code:
***********************
Module MainModule
Dim frm1 As New frmLogin1()

Sub Main()
If PrevInstance() Then
msg = "This Program is already running. Please shut down the currently running"
msg = msg & " process before starting a new one"
MsgBox(msg, vbInformation)
Exit Sub
Else
Startapplication()
End If
End Sub

Function PrevInstance() As Boolean
If UBound(Diagnostics.Process.GetProcessesByName(Diagnostics.Process.GetCurrentProcess.ProcessName)) > 0 Then
Return True
Else
Return False
End If
End Function

Sub Startapplication()
frm1.Show()
End Sub
End Module
**********************************

And I changed the startup object to "sub main" in the project property.

Now, when I do F5, the frmLogin shows, and then disappear automatically...

Can anybody tell me what I did wrong? many thanks...

If you use a Main method then the application exits when the Main method completes. If you call Show on a form, as soon as the form is displayed the method returns. This means that the Main method then completes and your app exits, hence the form closes. That is why you call Application.Run with an instance of your form class rather than Show, e.g.:

Code:

---

Application.Run(frm1)

---

Application.Run does not return until the form it was passed is closed.

Thank you very much...

that or showdialog instead

ShowDialog is for showing a dialogue. Application.Run is for running an application. While ShowDialog may appear to do the same thing it is more correct to call Application.Run in this case.

The point here is to stop the thread both do it. But in any case, do application.run..