Question

I have a background worker that calls a form, holding a gif animation. The purpose is to display the animation while process is underway but it should close when the process is done. But it does not close even after completion of the process. Please help.
Thanks

Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    frmAnimation.ShowDialog()
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    BackgroundWorker1.RunWorkerAsync()
    Dim sqldatasourceenumerator1 As SqlDataSourceEnumerator = SqlDataSourceEnumerator.Instance
    datatable1 = sqldatasourceenumerator1.GetDataSources()
    DataGridView1.DataSource = datatable1

    'I have tried CancelAsync, but did not work

    BackgroundWorker1.CancelAsync()
    frmAnimation.Dispose()
End Sub

Answer 1

BackgroundWorkers are intended to actually do the “work” of the background operation, so the main UI thread can continue rendering things onto the screen. I suspect you want the GetDataSources() function call to be done within the BackgroundWorker thread.

Try switching what’s in your button click function and what’s in the DoWork function of your BackgroundWorker. Specifically, I mean something like this:

    Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
            Dim sqldatasourceenumerator1 As SqlDataSourceEnumerator = SqlDataSourceEnumerator.Instance
            datatable1 = sqldatasourceenumerator1.GetDataSources()
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
            BackgroundWorker1.RunWorkerAsync()
            frmAnimation.ShowDialog()
    End Sub

And in addition, add some code to the RunWorkerCompleted event to handle what should be done upon completion of your background operation.

    Private Sub BackgroundWorker1_RunWorkerCompleted(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
            DataGridView1.DataSource = datatable1
            frmAnimation.Close()
    End Sub

You may also want to consider using frmAnimation.Show() instead of frmAnimation.ShowDialog() depending on if you want the procedure to be modal or modeless. You can read more about that here.