Running Different Processes In Multiple Threads Without Overlapping In VB.NET 2 - vb.net

Question

I have a sub-procedure which I want to run a different process, depending on what is currently running. I thought the easiest way to do this was by using an ArrayList of each of the campaign details & adding an 'Inuse' field to check to see if the Inuse field is set to 0 or 1. The problem that I have is that when running the process it is all happening at once & the integer hasn't been changed before the next thread kicks in so my threads are running the same campaigns.
I tried to avoid the problem by adding a Thread.Sleep(100) delay inbetween starting threads but this led to exactly the same problem.
Here's an example of what I am trying to do:
Imports System.Threading
Public Class Form1
Private Campaigns As New ArrayList
Private ProcessRunning As Boolean = False
Friend StopProcess As Boolean = False
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
For i = 0 To Campaigns.Count - 1
Dim objNewThread As New Thread(AddressOf RunProcess)
objNewThread.IsBackground = True
objNewThread.Start()
Next
End Sub
Private Sub UpdateCells(ByVal CampID As Integer, ByVal Column As String, ByVal newText As String)
Dim CellItemNum As Integer
If Column = "Status" Then CellItemNum = 4
DataGridView2.Rows(CampID).Cells.Item(CellItemNum).Value = newText
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
For i As Integer = 0 To 10
Campaigns.Add({Campaigns.Count(), "Campaign " & i, "Keywords " & i, "Link " & i, 5, True, 0, 0})
Next
DataGridView2.Rows.Clear()
For Each Campaign In Campaigns
DataGridView2.Rows.Add(New String() {Campaign(1), Campaign(2), Campaign(3), Campaign(6), ""})
Next
End Sub
Private Sub RunProcess()
' Set Variables
Dim CampID As Integer
Dim CampName As String
Dim Keywords As String
Dim Link As String
Dim CheckEvery As Integer
Dim OkToUse As Boolean
Dim Sent As Integer
' Find A Free Campaign
For i As Integer = 0 To Campaigns.Count - 1
' Check If Inuse
If Campaigns(i)(7) = 1 Then Continue For Else Campaigns(i)(7) = 1 ' This Line Sets Campaign To Inuse
' Most of the time only campaign(0) and campaign(1) are selected & multiple threads are running them instead of choosing unique campaigns
' Set Campaign Details
CampID = Campaigns(i)(0)
CampName = Campaigns(i)(1)
Keywords = Campaigns(i)(2)
Link = Campaigns(i)(3)
CheckEvery = Campaigns(i)(4)
OkToUse = Campaigns(i)(5)
Sent = Campaigns(i)(6)
' Start Process
UpdateCells(CampID, "Status", "Looking Up New Links (" & CampID & ")")
Exit For
Next
While StopProcess = False
Thread.Sleep(1000)
UpdateCells(CampID, "Status", "Running Process (" & CampID & ")")
Thread.Sleep(1000)
For i = 0 To CheckEvery
UpdateCells(CampID, "Status", "Re-Checking In " & (CheckEvery - i) & " Seconds")
Thread.Sleep(1000)
Next
End While
' Closing Processes
Campaigns(CampID)(7) = 0
End Sub
End Class

Answer 1

You can use SyncLock to force your threads to wait.
class level so all threads access same lock
private myLock as new Object
Then use syncLock when you start your process and end it when you are done.
SyncLock myLock
'process code here
End SyncLock
More MSDN info on the subject

Answer 2

Try looking into QueueUserWorkItem():
Private Sub Button1_Click(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles Button1.Click
For i = 0 To Campaigns.Count - 1
ThreadPool.QueueUserWorkItem(New WaitCallback(AddressOf RunProcess), Campaigns[i])
Next
End Sub
Then change the RunProcess() method to include the Campaign object sent in by the work item:
Private Sub RunProcess(ByVal o As System.Object)
' Process the Campaign
Dim campaign As Campaign = Ctype(o, Campaign)
End Sub
There will be no need for inuse, plus threads will be managed by the managed ThreadPool!