Question

I have a class written in C#. In it I want to run a certain function in parallel on a list. After it completes on each item I would like to update a progress bar. However, I get very odd behavior from my program. It executes the event and reaches my sub but never proceeds to actually execute any code. Instead it just freezes. (I’ve mixed vb.net and c#. It will be rewritten at some point)

so in my windows form I call

    progressBar.Visible = True
    progressBar.Value = 0
    progressBar.Maximum = dataGrid.SelectedRows.Count

    AddHandler quoteManager.refreshStarted, AddressOf progressBarCounter
    quoteManager.refreshAllAsync(list)

and the event is simply

Private Sub progressBarCounter()
    Me.Invoke(Sub()
                  If progressBar.Value = progressBar.Maximum Then
                      progressBar.Visible = False
                  Else
                      progressBar.Value += 1
                  End If
              End Sub)
End Sub

and in the quote manager class I have this defined.

    public event Action refreshStarted;

    public void refreshAllAsync(List<BindableQuote> bindableQuotes)
    {
        bindableQuotes.AsParallel()
            .WithDegreeOfParallelism(10)
            .ForAll((quote) => {
                quote.refreshAll();
                if (refreshStarted != null) { refreshStarted(); }
            });
    }

So for some reason I get it to enter progressBarCounter on each item in the list but it never exists. Instead it just keeps the form frozen.

Answer 1

I am not exactly sure this is what is happening, but it looks like progressBarCounter is blocking because you are calling Invoke. Should you be using BeginInvoke instead? Using BeginInvoke might solve the deadlock issue. See this post: What's the difference between Invoke() and BeginInvoke()