Question

I’m downloading a file using the following:

Dim client As WebClient = New WebClient()
client.DownloadFileAsync(New Uri("http://cachefly.cachefly.net/100mb.test"), "C:\Users\Dir\100mb.test")

The file downloads and saves into the C://Users/Dir/100mb.test, but while its downloading I would like to display the download speed in a label. How can I do this? I have read many tutorials, but most of them doesn’t works or are outdated. I’m a newbie with vb.net, so I can’t really write something on my own, could you give me any solutions?

Answer 1

May I suggest something different?

Imports System.Net

Public Class Form1

Private tmp = IO.Path.Combine(My.Computer.FileSystem.SpecialDirectories.Temp, "snafu.fubar")
Private Downloading As Boolean = False

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    If Downloading Then Exit Sub
    Downloading = True

    Dim wc As New WebClient
    AddHandler wc.DownloadProgressChanged, AddressOf wc_ProgressChanged
    AddHandler wc.DownloadFileCompleted, AddressOf wc_DownloadDone

    wc.DownloadFileAsync(New Uri("http://cachefly.cachefly.net/100mb.test"), tmp, Stopwatch.StartNew)

End Sub

Private Sub wc_DownloadDone(sender As Object, e As System.ComponentModel.AsyncCompletedEventArgs)
    Downloading = False
End Sub

Private Sub wc_ProgressChanged(sender As Object, e As DownloadProgressChangedEventArgs)
    Me.Label1.Text = (e.BytesReceived / (DirectCast(e.UserState, Stopwatch).ElapsedMilliseconds / 1000.0#)).ToString("#")
End Sub

End Class

Because it makes no sense to determine the speed by the last chunk of bytes received, but instead you measure the total number of bytes and divide by the TOTAL time. Passing a stopwatch instance to the eventhandler has the advantage that it doesnt ‘spoil’ your class code – it”s visible only where it’s needed.