[RESOLVED] 2nd thread does not end when flagged to end.

[MrJim547]

Good day,
When the main thread is busy, I want to display a progress bar and then close it when the main thread is finished work. The display of Form2 and it's progress bar work fine. But when the stopFlag is set, the 2nd thread does not see it and does not execute the Form2.Close() code. It only executes it after I manually close Form2. The below code is a simple app that demonstrates the problem. I am running Win 10 and VS 2019. Any ideas would be appreciated. Thanks

Imports System.Threading
Public Class Form1
    Dim stopFlag As Boolean = False
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        stopFlag = False
        Dim t = New Thread(AddressOf ShowProgress)
        t.Start()
        Dim y = 0
        For x = 1 To 10000
            While y < 200000
                y = y + 1
            End While
            y = 0
        Next
        stopFlag = True
        MessageBox.Show("Done")
    End Sub
    Private Sub ShowProgress()
        Form2.ShowDialog()
        Form2.BringToFront()
        While stopFlag = False
        End While
        Form2.Close()
    End Sub
End Class

[jmcilhinney]

You're doing it backwards. Display the ProgressBar on the main thread and do the work on the secondary thread. See here for a simple implementation that you can use as is.

[jmcilhinney]

As for your existing code, it's terrible. That While loop is what's known as a "busy wait", which means that, instead of actually waiting and doing nothing, the code is working at full throttle but not going anywhere or doing anything useful. That is something that you should NEVER do. At the very least, put a short delay inside the loop so that the code will actually wait there for a while instead of spinning incessantly.

Apart from that, the code can never even get to that loop as it is. Think about what ShowDialog actually does.