How to get a variable/value out of a thread?

[NeilF]

I want to write some code to do some processing. This seems best done in a thread. But I also want some UI and general controlling passed to and from it. eg: Adding lines to a text box for general UI updating while it's running.

Now, let's assume I might have multiple threads running, so each thread can call my UpdateUI subroutine. But the problem is, at the moment my code is using a public variable UI_Msg to pass values back from each thread to the UpdateUI subroutine. This hits me as dangerous as different threads may overwrite UI_Msg at the same time.

Instead I tryied to attach a class to each thread, so each thread has its own UI_Msg property/value. When I then get to UpdateUI, I want to pluck this value out of that thread, so there's no risk of different threads overwriting each others msgs to UpdateUI.


I've attached my code example.

So all I want to do is in UpdateUI, be able to look at UI_msg from the class for the thread calling UpdateUI. eg: Obtain thread.UI_msg for example...

Imports System.Threading

Public Class MainForm
    Public UI_msg As String

    ' Used to track which thread called the UI Update function.
    Private callingThread As Integer

    ' The Delegate that is invoked by the control on the form that needs to be updated.
    Delegate Sub UIDelegate()

    Private Sub UpdateUI()
        ' If InvokeRequired is true then the call is being made on a thread other
        ' than the UI thread.
        If Label1.InvokeRequired Then
            ' Call UpdateUI by invoking a delegate with the UI control
            callingThread = System.Threading.Thread.CurrentThread.ManagedThreadId()

            Dim newDelegate As New UIDelegate(AddressOf UpdateUI)
            Label1.Invoke(newDelegate)
        Else
            Label1.AppendText(Text + "Thread " + callingThread.ToString() + ":" + UI_msg + vbCrLf)
            ' ** How can I get the UI_MSG from the thread class? **
            UI_msg = ""
            Label1.ScrollToCaret()
        End If
    End Sub

    Private Sub StartJob_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles StartJob.Click
        UI_msg = "Starting a new thread"
        UpdateUI()

        Dim JobThread As New Thread(AddressOf RunJob)
        JobThread.Start()
    End Sub

    Class JobObjClass
        Public JobCanceled As Boolean
        Public UI_Msg As String
    End Class

    Sub RunJob()
        Dim StateObj As New JobObjClass()
        StateObj.JobCanceled = False

        Dim ctr As Integer
        ctr = 0
        While (ctr < 5 And abort = False)
            System.Threading.Thread.Sleep(1000)
            ctr = ctr + 1
            UI_msg = "Count " & ctr.ToString()
            StateObj.UI_Msg = "Count " & ctr.ToString() ' ** Want to use this instead of previous line!
            UpdateUI()
        End While

        StateObj.JobCanceled = True
        UI_msg = "Ending thread"
        UpdateUI()
    End Sub


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        abort = True
    End Sub
End Class

I hope this makes sense... I'm only a week or so into Visual Basic.