Using RunWorkerAsync in my download program

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  12 years ago

  by mecablaze

  First Last

  Washington D.C., United States

  Joined 12 years ago
  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 [http://i37.tinypic.com/208y1xd.jpg](http://i37.tinypic.com/208y1xd.jpg) 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.
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  12 years ago

  by James Crowley

  James Crowley

  London, United Kingdom

  Joined 20 years ago
  Hi there, Welcome to developerFusion! Multi-threading can take a while to wrap your head around... This code snippet might help you get started: [Easy Asyncronous programming](http://www.developerfusion.com/code/4689/easy-asynchronous-programming/) and [Really simple multithreading Windows Forms](http://www.mikedub.net/mikeDubSamples/SafeReallySimpleMultithreadingInWindowsForms20/SafeReallySimpleMultithreadingInWindowsForms20.htm) If you want something more in-depth, there's [Multithreading in VB.NET](http://www.developerfusion.com/article/5184/multithreading-in-vbnet/) too. Hope that helps!
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