Question Using RunWorkerAsync in my download program

[mecablaze]

Hello,

Right now I'm writing a program that can download a file from the a URL provided in a text box. Here's my code so far.

Imports System.IO 
Imports System.Net 
 
Public Class Download 
    Delegate Sub updateProgressBarDelegate(ByVal percent As Integer) 
 
    Private Sub downloadButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles downloadButton.Click 
        downloadFile(url.Text, fileName.Text) 
    End Sub 
 
    Private Sub downloadFile(ByVal url As String, ByVal fileName As String) 
        Dim webRequest As HttpWebRequest 
        Dim webResponse As HttpWebResponse 
        Dim writeStream As New IO.FileStream(fileName, IO.FileMode.Create) 
 
        webRequest = HttpWebRequest.Create(url) 
        webResponse = webRequest.GetResponse() 
 
        Dim fileSize As Integer 
        fileSize = webResponse.ContentLength 
        Dim nRead As Integer 
        nRead = 0 
        Dim buffer(4096) As Byte 
        Dim blockSize As Integer 
        Dim tempStream As New MemoryStream 
 
        Dim updateProgressBarDelegateSafe As New updateProgressBarDelegate(AddressOf updateProgressBar) 
        Invoke(updateProgressBarDelegateSafe, 0) 
 
        Do 
            Dim readBytes(4095) As Byte 
            blockSize = writeStream.Read(buffer, 0, 4096) 
            Dim bytesread As Integer = webResponse.GetResponseStream.Read(readBytes, 0, 4096) 
            nRead += bytesread 
            If bytesread = 0 Then Exit Do 
            writeStream.Write(readBytes, 0, bytesread) 
            Dim percent As Short = (nRead * 100) / fileSize 
            Invoke(updateProgressBarDelegateSafe, percent) 
        Loop 
        webResponse.Close() 
        writeStream.Close() 
    End Sub 
 
    Public Sub updateProgressBar(ByVal percent As Integer) 
        downloadProgress.Value = percent 
    End Sub 
End Class

Here's a screen shot of the layout. The top text box is where you type in the URL, the second is where you type in the file name and the three white bar is a progress bar. When you press the "Download!" button it begins the download.

As of now, when you hit the button, the window locks up and does not respond until the download is complete. Is there a way to use multithreads to make the download work in the background so I could make a Cancel button work in the program? I did my research and found a little method called RunWorkerAsync. I read up on it but was baffled on how to actually use it in my situation.

Any suggestions?

Thanks for your help in advance.

 

[JohnH]

Look up BackgroundWorker Class. Basic setup: Add one to form from toolbox, dblclick it and add worker code. Use for example a button to battle the BGW.RunWorkerAsync method.