Producer & Consumer Model - use Queue, Threadpool

Imports System.Threading Public Class Form1 Private Queue1 As New Queue(Of String()) Private cts As New CancellationTokenSource() Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click If Button1.Text.Contains("Start") Then Dim w1 As WaitCallback = New WaitCallback(AddressOf producer) Dim w2 As WaitCallback = New WaitCallback(AddressOf consumer) Dim w3 As WaitCallback = New WaitCallback(AddressOf consumer2) Dim w4 As WaitCallback = New WaitCallback(AddressOf consumer3) ThreadPool.QueueUserWorkItem(w1, cts.Token) ThreadPool.QueueUserWorkItem(w2, cts.Token) ThreadPool.QueueUserWorkItem(w3, cts.Token) ThreadPool.QueueUserWorkItem(w4, cts.Token) Button1.Text = "Thread Stop" Else cts.Cancel() Button1.Text = "Thread Start" End If End Sub Sub producer(ByVal arg As Object) Dim token As CancellationToken = CType(arg, CancellationToken) Dim Array(50) As String While 1 = 1 If token.IsCancellationRequested Then Exit While Else Monitor.Enter(Queue1) Queue1.Enqueue(Array) Monitoring(1) Monitor.Exit(Queue1) Thread.Sleep(5) End If End While End Sub Sub consumer(ByVal arg As Object) Dim token As CancellationToken = CType(arg, CancellationToken) While 1 = 1 If token.IsCancellationRequested Then Exit While Else Monitor.Enter(Queue1) If Queue1.Count > 0 Then Queue1.Dequeue() Monitoring(1) Monitor.Exit(Queue1) Thread.Sleep(15) End If End While End Sub Sub consumer2(ByVal arg As Object) Dim token As CancellationToken = CType(arg, CancellationToken) While 1 = 1 If token.IsCancellationRequested Then Exit While Else Monitor.Enter(Queue1) If Queue1.Count > 0 Then Queue1.Dequeue() Monitoring(1) Monitor.Exit(Queue1) Thread.Sleep(15) End If End While End Sub Sub consumer3(ByVal arg As Object) Dim token As CancellationToken = CType(arg, CancellationToken) While 1 = 1 If token.IsCancellationRequested Then Dim QCnt As Integer = Queue1.Count For i As Integer = 0 To QCnt - 1 Queue1.Dequeue() Monitoring(1) Next Exit While Else Monitor.Enter(Queue1) If Queue1.Count > 0 Then Queue1.Dequeue() Monitoring(1) Monitor.Exit(Queue1) Thread.Sleep(15) End If End While End Sub Private Delegate Sub AppendTextBoxDelegate(ByVal ThreadNum As Integer) Private Sub Monitoring(ThreadNum As Integer) If ThreadNum = 1 Then If Txt_Th1_1.InvokeRequired Then Txt_Th1_1.Invoke(New AppendTextBoxDelegate(AddressOf Monitoring), New Object() {ThreadNum}) Else Txt_Th1_1.Text = Queue1.Count End If End If End Sub End Class