VB.NET AddHandler Download Progress for multiple files - vb.net

Question

I trying to write an app to download 2 files, I'm able to download the 2 files with the code below:
Dim client As WebClient = New WebClient
AddHandler client.DownloadProgressChanged, AddressOf client_ProgressChanged
AddHandler client.DownloadFileCompleted, AddressOf client_DownloadCompleted
client.DownloadFileAsync(New Uri("http://URL.com/Myfile.exe"), "..\MyFile.exe")
Button1.Text = "Download in Progress"
Button1.Enabled = False
Dim client2 As WebClient = New WebClient
AddHandler client2.DownloadProgressChanged, AddressOf client_ProgressChanged
AddHandler client2.DownloadFileCompleted, AddressOf client_DownloadCompleted
client2.DownloadFileAsync(New Uri("http://URL.com/Myfile2.exe"), "..\MyFile2.exe")
Problem I'm having is that the progress bar is not showing total download progress for both files. It shows one, then a few seconds later shows the other one and keeps switching between both.
Private Sub client_ProgressChanged(ByVal sender As Object, ByVal e As DownloadProgressChangedEventArgs)
Dim bytesIn As Double = Double.Parse(e.BytesReceived.ToString())
Dim totalBytes As Double = Double.Parse(e.TotalBytesToReceive.ToString())
Dim percentage As Double = bytesIn / totalBytes * 100
ProgressBar.Value = Int32.Parse(Math.Truncate(percentage).ToString())
Label1.Text = "Downloaded: " & bytesIn & " of " & totalBytes
Label2.Text = String.Format("{0:00}", percentage) & "%"
End Sub
Anyone know how I can make the progressbar have the values of both downloads combined? Or maybe how I can tell it to wait for the first download then start the second?

Answer 1

You simply need to keep track of progress for each WebClient. Total progress is going to be 200%. Solving it for the general case:
Dim progress As Dictionary(Of WebClient, Integer)
Sub StartDownloads()
progress = new Dictionary(Of WebClient, Integer)
Dim client As WebClient = New WebClient()
progress.Add(client, 0)
'' etc..
End Sub
Private Sub client_ProgressChanged(ByVal sender As Object, ByVal e As DownloadProgressChangedEventArgs)
progress(DirectCast(sender, WebClient)) = e.ProgressProcent
Dim total As Integer = 0
For Each client In progress.Keys
total += progress(client)
Next
ProgressBar.Value = total \ progress.Count
End Sub
Untested, ought to be close.

Answer 2

To make it load one file at a time, use a List(Of String) for all the files names. Start the process using the first element(filename) use the completed event and remove that file name and the addhandler for the completed event. Then check if there are more files in the List(Of String) then charge up a new WebClient for that one - rinse repeat.
Private files As New List(Of String)
'fill this with the file names(URIs) then start the process
Private Sub DownloadFile()
Dim client As New WebClient
AddHandler client.DownloadProgressChanged, AddressOf client_ProgressChanged
AddHandler client.DownloadFileCompleted, AddressOf client_DownloadCompleted
client.DownloadFileAsync(New Uri(files(0), "some destination path")
End Sub
Private Sub client_DownloadCompleted(...)
RemoveHandler client.DownloadProgressChanged, AddressOf client_ProgressChanged
RemoveHandler client.DownloadFileCompleted, AddressOf client_DownloadCompleted
files.RemoveAt(0)
If files.Count > 0 Then DownloadFile()
End Sub