Method to download large files in Vb.net - vb.net

Question

Okay, so I have been trying to download a large file with different methods. In my code what would usually work best is My.Computer.NetWork.DownloadFile but because the file is 1.5Gb's my windows form freezes and doesn't respond. I didn't bother waiting to see for how long it wouldn't respond for after I waited 5 minutes because I thought it would just be a waste of time. So I also tried wc.DownloadFileAsync (wc standing for Web Client) this works and doesn't freeze my windows form but the problem with this is that it skips over it and doesn't wait until the download is finished so it continues on with my code and therefore I get errors.
I tried researching ways to pause or stop the code until the download was finished but no luck. After further research I found the backgroundworker class. I was wondering if this would work for me and how would I implement it into my code, or if there is any easier way to go about doing this?
I was not able to successfully implement it into my code. I wasn't able to invoke and therefore got errors such as this: Cross-thread operation not valid.
This is currently my code, with the background worker:
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Dim downloader As New System.Net.WebClient
Dim ServerVersion = wc.DownloadString("http://127.0.0.1:8080/patch/PatchList.txt").Trim
Dim tLines As String() = ServerVersion.Split(Environment.NewLine)
For Each NewLine As String In tLines
Dim tVersionAndUrl As String() = NewLine.Split(vbTab)
Dim encText As New System.Text.UTF8Encoding()
Dim btText() As Byte
btText = encText.GetBytes(tVersionAndUrl(0))
'MessageBox.Show(btText.ToString)
'MessageBox.Show(tVersionAndUrl(0)(0))
If tVersionAndUrl.Length < 2 Then
Exit For
End If
If Integer.Parse(tVersionAndUrl(0)) < Integer.Parse(CVersion.Text) Then
Dim TempPath As String = "\launcher\temp.rar"
AddHandler wc.DownloadProgressChanged, AddressOf ProgressChanged
AddHandler wc.DownloadProgressChanged, AddressOf ProgressChanged
AddHandler wc.DownloadFileCompleted, AddressOf DownloadCompleted
'wc.DownloadFileAsync(New Uri(tVersionAndUrl(1)), Me.GetFileName(tVersionAndUrl(1)))
wc.DownloadFileAsync(New Uri(tVersionAndUrl(1)), tmp, Stopwatch.StartNew)
'My.Computer.FileSystem.DeleteFile(Me.GetFileName(tVersionAndUrl(1)))
CVersion.Text = tVersionAndUrl(0)
LabelStatus.Text = "Download in Progress"
Button1.Enabled = False
End If
Next
MsgBox("Client is up to date")
End Sub
And this is the Addhandlers for it:
Private Sub 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
ProgressBarCurrent.Value = Int32.Parse(Math.Truncate(percentage).ToString())
Dim BytesDownloaded As String = (e.BytesReceived / (DirectCast(e.UserState, Stopwatch).ElapsedMilliseconds / 1000.0#)).ToString("#")
If BytesDownloaded < 1024 Then
Dim Bs As String = Convert.ToInt32(BytesDownloaded)
Label4.Text = (Bs & " B/s")
ElseIf BytesDownloaded < 1048576 Then
Dim KBs As String = Math.Round(BytesDownloaded / 1024, 2)
Label4.Text = (KBs & " KB/s")
ElseIf BytesDownloaded < 1073741824 Then
Dim MBs As String = Math.Round(BytesDownloaded / 1048576, 2)
Label4.Text = (MBs & " MB/s")
End If
End Sub
Private Sub DownloadCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.AsyncCompletedEventArgs)
'MessageBox.Show("Download Complete")
LabelStatus.Text = "Download Complete"
Button1.Enabled = True
Downloading = False
End Sub
I would appreciate any help. Thanks.

Answer 1

In newer VB/C# .net the keywords you are interested in are Await and Async:
http://msdn.microsoft.com/en-us/library/vstudio/hh191443.aspx?cs-save-lang=1&cs-lang=vb#code-snippet-1
Also you should design your routine to download in chunks. There are many ways to do that but maybe you are better to look at HTTPWebRequest/Response will handles chunking and has a method to work with +2GB files easily (ranging).
Sorry not an answer as I don't have enough rep to put this as a comment.
Cheers,
Al

Answer 2

In your code, we can see that you have used BackgroundWorker class, which seems good to me. What i am trying to find is the remaining delegate functions of the BackgroundWorker class like ProgressChanged, RunWorkerCompleted (instead you have registered you own delegates which might seems to lead to an error on the later stage). Try handling these events, it should help you and let you know when the task completes and reports progress in the meanwhile. For reporting progress, in the main UI thread, you can also run a progress bar with style property set as Marquee.