Question

I’m trying to thread my functions so the main GUI of my application doesn’t fail to respond while the tasks are running.

At the moment my form1.vb is something like this. I’ve cut it down as to reduce the text, but everything works fine:

Public Class MAIR

Private Sub InstallTheAgent_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles InstallTheAgent.Click
    InstallAgentWorker.RunWorkerAsync()
End Sub

Private Sub InstallAgentWorker_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles InstallAgentWorker.DoWork
'Do some stuff
End Sub

Private Sub InstallAgentWorker_RunWorkerCompleted(ByVal sender As System.Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles InstallAgentWorker.RunWorkerCompleted
    ' Called when the BackgroundWorker is completed.
    MsgBox("Installation of the Agent Complete")
    ProgressBar1.Value = 0
End Sub

End Class

From my understanding, when the button “Open” is pressed, it calls the function Install and it should start this off in a separate thread, however this doesn’t work.

This seems to work, but the GUI still locks up, suggesting its not in a separate thread

Answer 1

I recommend using the BackgroundWorker Class to implement this kind of basic threading. You don’t have a lot going on here so the basic implementation should suffice. Here is a snippet of how I would go about doing it. My method is a bit too complex (I have base classes and events wired up to catch a lot of worker events) to list here succinctly, so I’ll abbreviate.

Public Class MAIR

    Dim worker as BackgroundWorker

    Private Sub Open_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Open.Click
        worker.RunWorkerAsync()
    End Sub

    Protected Sub Worker_DoWork(ByVal sender as Object, ByVal e as DoWorkEventArgs)
        Call Shell("psexec.exe", AppWinStyle.Hide, True)       
    End Sub

    Protected Sub Worker_ProgressChanged(Byval sender as Object, ByVal e as ProgressChangedEventArgs)
        ' You can track progress reports here if you use them
    End Sub

    Protected Sub Worker_RunWorkerCompleted(Byval sender as Object, ByVal e as RunWorkerCompletedEventArgs)
        ' Report back to the main application that the thread is completed
    End Sub

    Private Sub Install_Load(ByVal sender As System.Object, ByVal e As System.EventArgs)     Handles MyBase.Load
        worker = New BackgroundWorker()

        ' Add the event wire-ups

        ' ### This event wire-up establishes the link
        ' ### that is used by RunWorkerAsync to initiate
        ' ### the code you want to run asynchronously
        AddHandler worker.DoWork, AddressOf Worker_DoWork

        AddHandler worker.ProgressChanged, AddressOf Worker_ProgressChanged
        AddHandler worker.RunWorkerCompleted, AddressOf Worker_RunWorkerCompleted
    End Sub

End Class

This is all translated from C#, so treat it as psuedo-code. The important piece is the documentation of the BackgroundWorker and its behaviors. There is a lot of terrific functionality in this class that takes the headaches of threads away for simple usages. This class is located in System.ComponentModel so you’ll need the reference and an Imports statement.

Edit: Something I forgot to mention is that once the worker is fired asynchronously, the only manner of tracking it or communicating with the main application is through the ProgressChanged and RunWorkerCompleted events. No global variables or cross-thread items will be available, so you’ll have to use the built-in properties to pass in any values (such as computerName it looks like) that you may need during the run.