BackgroundWorkers - ProgressChanged for static progress - vb.net

Question

I want to use a backgroundworker to poll a hardware sensor very frequently without leaving my UI inoperable.
Because the backgroundworker simply polls until interrupted - runtime is purely dictated by the user interrupting it - it has no change in progress so to speak.
If I call ReportProgress with a constant value, e.g. ReportProgress(1), will this still call ProgressChanged? I require ProgressChanged to update the UI in accordance with the latest poll data.

Answer 1

The value passed as first parameter to ReportProgress just serves at your code on the UI thread to display the advancement of your background task.
It has no importance for the execution of the call to ProgressChanged.
If you need to communicate some different data to your ProgressChanged event you could use the overload of ReportProgress that takes two arguments and allows to pass the instance of a custom object as second parameter.
In this very trivial example, I have defined a class named WorkingStatus with just one property that I change in the DoWork method, then I pass an instance of this class to the ProgressChanged event. Of course your WorkingStatus class could be more complex with all the informations that you want to display on the UI thread
public class WorkingStatus
public Current as Integer
'.... other properties as needed....
End Class
Sub Main
Dim bkw = new BackgroundWorker()
bkw.WorkerReportsProgress = true
AddHandler bkw.ProgressChanged, AddressOf bgw_ProgressChanged
AddHandler bkw.DoWork, AddressOf bgw_DoWork
bkw.RunWorkerAsync()
' This loop just to avoid the immediate close of the example
Dim counter = 0
While (bkw.IsBusy)
counter+=1
Console.WriteLine("IsBusy " & counter.ToString())
Thread.Sleep(150)
End While
End Sub
private sub bgw_DoWork(sender as object, e as DoWorkEventArgs)
Dim bgw = DirectCast(sender, BackgroundWorker)
Dim sts = new WorkingStatus() With {.Current = 0}
' A simulation of your inner working
for i = 0 to 10
Thread.Sleep(5000)
sts.Current+=1
bgw.ReportProgress(1, sts)
Next
Console.WriteLine("Background DoWork ENDED")
End Sub
private sub bgw_ProgressChanged(sender as object, e as ProgressChangedEventArgs)
Dim sts = DirectCast(e.UserState, WorkingStatus)
Console.WriteLine("Progress:" & e.ProgressPercentage.ToString() & ", Status=" & sts.Current)
End Sub