Vb.net multithreading not working...? - vb.net

Question

I'm trying to create a multithreaded program to poll machines for data but I can't seem to get it working correctly. The code below is working and is creating 4 threads as it should but the flow of the code seems to happen in series and on the main UI thread.
What I'm trying to achieve is for each row of the datagrid to update simultaneously without locking up the UI.
Below is a dumbed down version of what I have but it serves to demonstrate the problem.
For info the 'testclass' is a class used as an instance of a machine with each class element representing a property of a machine.
Hope I've given enough info to explain the problem. Thanks in advance.
Ps I shouldn't need to refresh form should I?
Imports System.Threading
Public Class TestForm
Public threadcount As Integer
Public Delegate Sub testclassDelegate(test As Object)
Private Class testclass
Public index As Integer
Public TestVal1 As Integer = 100
Public TestVal2 As Integer = 200
Public TestVal3 As Integer = 300
Public TestVal4 As Integer = 400
Public TestVal5 As Integer = 500
Public TestVal6 As Integer = 600
Public testDel As testclassDelegate
End Class
Private Sub TestForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load
For i As Integer = 0 To 3
DataGridView1.Rows.Add()
DataGridView1.Rows(i).Cells(0).Value = i + 1
Next
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
For i As Integer = 0 To 3
DataGridView1.Rows(i).Cells(1).Value = ""
DataGridView1.Rows(i).Cells(2).Value = ""
DataGridView1.Rows(i).Cells(3).Value = ""
DataGridView1.Rows(i).Cells(4).Value = ""
DataGridView1.Rows(i).Cells(5).Value = ""
DataGridView1.Rows(i).Cells(6).Value = ""
Next
Poll_FreeThread()
End Sub
Private Sub Poll_FreeThread()
For i As Integer = 0 To DataGridView1.Rows.Count - 1
Dim test As New testclass
test.index = i
test.testDel = AddressOf UIUpdate
Interlocked.Increment(threadcount)
Me.Label2.Text = threadcount
Try
Dim thPoll As New Thread(Sub() invokeUIUpdate(test))
thPoll.IsBackground = True
thPoll.Priority = ThreadPriority.BelowNormal
thPoll.Start()
Catch ex As Exception
MsgBox(ex.Message)
End Try
Next
End Sub
Public Sub invokeUIUpdate(test As Object)
If DataGridView1.InvokeRequired Then
DataGridView1.Invoke(New testclassDelegate(AddressOf UIUpdate), test)
Else
UIUpdate(test)
End If
End Sub
Public Sub UIUpdate(test As Object)
Thread.Sleep(test.index * 100)
DataGridView1.Rows(test.index).Cells(1).Value = test.TestVal1
Me.Refresh()
Thread.Sleep(100)
DataGridView1.Rows(test.index).Cells(2).Value = test.TestVal2
Me.Refresh()
Thread.Sleep(100)
DataGridView1.Rows(test.index).Cells(3).Value = test.TestVal3
Me.Refresh()
Thread.Sleep(100)
DataGridView1.Rows(test.index).Cells(4).Value = test.TestVal4
Me.Refresh()
Thread.Sleep(100)
DataGridView1.Rows(test.index).Cells(5).Value = test.TestVal5
Me.Refresh()
Thread.Sleep(100)
DataGridView1.Rows(test.index).Cells(6).Value = test.TestVal6
Me.Refresh()
Interlocked.Decrement(threadcount)
Me.Label2.Text = threadcount
End Sub
End Class

Answer 1

Run your code a little bit different, This is how the Structure should look like for Multithreading in vb.net ( it has something to do with Vb.net not passing Namespaces into Models from what i Understand )
This would be your startThread from MainThread in load or w/e have you
Private Sub DoSomethingSimple()
Dim DoSomethingSimple_Thread As New Thread(AddressOf DoSimple)
DoSomethingSimple_Thread.Priority = ThreadPriority.AboveNormal
DoSomethingSimple_Thread.Start(Me)
End Sub
This would be the actual thread Itself ( new model / class or in the same class )
Private Sub DoSimple(beginform As Form)
'Do whatever you are doing that has nothing to do with ui
'For UI calls use the following
SomethingInvoked(PassibleVariable, beginform)
End Sub
Write a Delegate and Invoke Method for Each Call to the Main Thread.
Delegate Sub SomethingInvoked_Delegate(s As Integer, beginform As Form)
Sub SomethingInvoked_Invoke(ByVal s As Integer, beginform As Form)
If beginform.NameOfControlYouAreUpdating.InvokeRequired Then ' change NameOfControlYouAreUpdating to the Name of Control on the form you wish to update
Dim d As New SomethingInvoked_Delegate(AddressOf SomethingInvoked_Invoke)
beginform.Invoke(d, New Object() {s, beginform})
Else
'Do something...
beginform.NameOfControlYouAreUpdating.Condition = Parameter
End If
End Sub
This is tested ( non hanging ) way of writing Threads in vb.net
If you need further help implementing your code to this Template let me know :P

Answer 2

You can use timer and backgroundworker with event of DoWorkEventHandler and RunWorkerCompletedEventHandler.
Example: C# example:
private void Button1_Click(object sender, EventArgs e)
{
workerThreadForLetters.WorkerReportsProgress = true; workerThreadForLetters.WorkerSupportsCancellation = true;
workerThreadForLetters.DoWork -= new DoWorkEventHandler(workerThreadForLetters_DoWork);
workerThreadForLetters.DoWork += new DoWorkEventHandler(workerThreadForLetters_DoWork);
workerThreadForLetters.RunWorkerCompleted -= new RunWorkerCompletedEventHandler(workerThreadForLetters_RunWorkerCompleted);
workerThreadForLetters.RunWorkerCompleted += new RunWorkerCompletedEventHandler(workerThreadForLetters_RunWorkerCompleted);
}
private void workerThreadForLetters_DoWork(object sender, DoWorkEventArgs e)
{
//DO SOMETHING
}
private void workerThreadForLetters_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
//DO AS REQUIRED
Timer1.enable = false;
}
private void tmCollectionLettersUpdate_Tick(object sender, EventArgs e)
{
//Content update like % of data progressed or any.
}