Modifying Labels and Objects in Forms from Classes (VB.NET) - vb.net

Question

I have a class that gets the internet time and displays it in a text box. This is that class name InternetTimeGet
I have added a "progress meter" in that class that will show how far through the list of IPs the program is. Right now the Debug Console is displaying these IPs and updates fine as is shown here: IPs and Progress
Everything is already multithreaded and nothing is hanging my UI
However, I'm having trouble getting the program to display the progress on a label named ProgLbl in my main form named MainForm. Here is the code of my InternetTimeGet class:
Public Class InternetTimeGet
'Irrelevant variables omitted...
'Used to update progress
Public Shared IPCount As Integer
Public Shared ProgDivision As Single
Public Shared ProgBar As Single
Public Shared FullBar As Integer = 100
IPCount = My.Settings.ServerIPList.Count
ProgDivision = FullBar / IPCount
For Each IP As String In ServArray
Try
'Shows each IP and the Percentage completion in Debug console
Debug.WriteLine(IP, "IP Addresses")
ProgBar = ProgBar + ProgDivision
Debug.WriteLine(Math.Round(ProgBar, 1) & "%", "Progress")
MainForm.ProgLbl.Text = "Progress: " & Math.Round(ProgBar, 1) & "%"
If My.Computer.Network.Ping(IP) Then
LastHost = IP
Result = GetNISTTime(IP)
End If
Catch ex As Exception
'Return "Sync Error 0x01"
MsgBox("There was a sync error while retrieving the updated internet time. Please try again.", MsgBoxStyle.Critical, "Sync Error 0x01")
Debug.WriteLine("There was a sync error while retrieving the updated internet time. Please try again.", "Sync Error 0x01")
End Try
Next
The Debug console shows each IP and the percentage of completion fine and does not not show intermediate updates or hang the UI, but the label ProgLbl in my main form MainForm does not show these updates at all and just remains saying "Progress: ". Once again my main form MainForm's UI DOES NOT hang.
The problem is updating the label, ProgLbl, in my main form, MainForm, from the InternetTimeGet class shown above. That's what I'd appreciate help with.
I have been looking for an answer and tried several things but finally gave up and decided to ask those who know better.
Thank you for your help

Answer 1

Well, it is not clear where your code is implemented but if you want to make some operation (such as getting time and going through a list of IPs), as a general rule, you'll want to avoid to do it in the main thread to avoid freezing the UI.
The background worker is perfect for that kind of purpose, as it will allow you to run code Async while reporting progress so you can update your main form.
Here is a simple example using a background worker
that you will have to rework to fit your need.
Private WithEvents _GetTimeWorker As BackgroundWorker
Somewhere in your form, you need to initialize your worker and set the WorkerReportProgress to true. You can then start the worker when you need.
Private Sub MainWindow_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
_GetTimeWorker = New BackgroundWorker With {.WorkerReportsProgress = True}
_GetTimeWorker.RunWorkerAsync()
End Sub
DoWork is actually the async method that you put your logic in so it does not block the UI. When you want to update the progress bar, you call ReportProgress on your background worker.
Private Sub _GetTimeWorker_DoWork(sender As Object, e As DoWorkEventArgs) Handles _GetTimeWorker.DoWork
Dim watch As New Stopwatch
watch.Start()
'Just simulating some work.
While watch.ElapsedMilliseconds < 10000
System.Threading.Thread.Sleep(100)
_GetTimeWorker.ReportProgress(CInt(watch.ElapsedMilliseconds / 10000 * 100))
End While
End Sub
The progress bar value is updated from the progress changed function.
Private Sub _GetTimeWorker_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles _GetTimeWorker.ProgressChanged
'There we change the progress bar value
prog1.Value = e.ProgressPercentage
End Sub