Question

I have a case where i need to generate millions of unique codes. For this I have created a generate function where the random number is generated. I call this function from a for loop and add the generated number on a list box. my code is as follow

  for i=1 to val(txtnumber.txt)
       mynum=generate()
  next

I have created a lable on form where i wanted to display the no of secs elapsed while processing the loop. I used timer control as

     timer1.start()
     for i=1 to val(txtnumber.text)
        mynum=generate()
        listbox1.items.add(mynum)
     next
     timer1.stop

and on timer1_tick function

     Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
    Label1.Text = Val(Label1.Text) + 1
     End Sub

but when i click generate button, all numbers are generated, but timer doesnot shows time elapsed.

I may have missed something, so please help me out

Answer 1

This is probably best handled in a BackgroundWorker. Place one on the form and set its WorkerReportsProgress=True. Also, placing a million numbers in a ListBox probably isn’t a good idea, so I omitted that.

Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
  Button1.Enabled = False
  BackgroundWorker1.RunWorkerAsync()
End Sub

Private Sub BackgroundWorker1_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
  Dim started As DateTime = Now
  For i As Integer = 1 To val(txtnumber.txt)
    mynum=generate()
    BackgroundWorker1.ReportProgress(i, Nothing)
  Next
  Dim ended As TimeSpan = Now.Subtract(started)
  BackgroundWorker1.ReportProgress(0, ended.TotalSeconds.ToString)
End Sub

Private Sub BackgroundWorker1_ProgressChanged(ByVal sender As Object, ByVal e As ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
  If e.UserState IsNot Nothing Then
    Label1.Text = e.UserState.ToString()
  Else
    Label1.Text = e.ProgressPercentage.ToString
  End If
End Sub

Private Sub BackgroundWorker1_RunWorkerCompleted(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
  Button1.Enabled = True
End Sub

Your label should be updating correctly when the worker reports the ProgressChanged event.