Develop Reference

DownloadFileAsync is blocking my App

I am trying to download a large file(around 1GB) my server.When I start downloading I am unable to use the app till the download completes. It is blocking the UI and its becoming unresponsive.
In below code I am calling DownloadFile method when the user download button on the UI.And then download starts, but the UI is freezed.
I read that DownloadFileAsync won't block the UI. But here its blocking. How to use it in correct way. There are several answers but none is working when I am testing.
Code:
Button call:
private void Button_Click(object sender, RoutedEventArgs e)
{
Debug.WriteLine("1");
DownloadGamefile DGF = new DownloadGamefile();
Debug.WriteLine("2" + Environment.CurrentDirectory);
DGF.DownloadFile("URL(https link to zip file)", Environment.CurrentDirectory + #"\ABC.zip");
Debug.WriteLine("3");
}
Download code:
class DownloadGamefile
{
private volatile bool _completed;
public void DownloadFile(string address, string location)
{
WebClient client = new WebClient();
Uri Uri = new Uri(address);
_completed = false;
client.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed);
client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(DownloadProgress);
client.DownloadFileAsync(Uri, location);
}
private void DownloadProgress(object sender, DownloadProgressChangedEventArgs e)
{
// Displays the operation identifier, and the transfer progress.
Console.WriteLine("{0} downloaded {1} of {2} bytes. {3} % complete...",
(string)e.UserState,
e.BytesReceived,
e.TotalBytesToReceive,
e.ProgressPercentage);
}
private void Completed(object sender, AsyncCompletedEventArgs e)
{
if (e.Cancelled == true)
{
Console.WriteLine("Download has been canceled.");
}
else
{
Console.WriteLine("Download completed!");
}
_completed = true;
}
}

Please refer to this link. The actual problem is getting lots of feedback about the number of bytes downloaded(about progress of download process). Take a timer to get progress for every 2 seconds or any time, this solved the problem.

Downloading multiple files one at a time

This is the Code Below....
using System.Net;
//Create Temporary Folder to Holde All the Downloads............
namespace downloadFileCSharp10
{
public partial class Form1 : Form
{
string url = "URL";
string path = #"c:\Folder";
public Form1()
{
InitializeComponent();
}
void InitiateDownload(string RemoteAddress, string LocalFile, AsyncCompletedEventHandler CompleteCallBack, object userToken)
{
WebClient wc = new WebClient();
wc.DownloadProgressChanged += wc_DownloadProgressChanged;
wc.DownloadFileCompleted += wc_DownloadFileCompleted;
wc.DownloadFileAsync(new Uri(RemoteAddress), LocalFile, userToken);
}
void wc_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
{
if (e.Error != null)
{
lblInfo1.Visible = true;
lblInfo1.ForeColor = Color.Red;
lblInfo1.Text = "Error Downloading ";
//throw e.Error;
}
else if (e.Cancelled)
{
lblInfo1.Visible = true;
lblInfo1.ForeColor = Color.Red;
lblInfo1.Text = "Download Cancelled " + e.UserState + e.Error;
}
else
{
lblInfo1.Visible = true;
lblInfo1.ForeColor = Color.Red;
lblInfo1.Text = e.UserState + " Download Complete!! ";
}
//throw new NotImplementedException();
}
void wc_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
double bytesIn = double.Parse(e.BytesReceived.ToString());
double totalBytes = double.Parse(e.TotalBytesToReceive.ToString());
double percentage = bytesIn / totalBytes * 100;
progressBar1.Value = int.Parse(Math.Truncate(percentage).ToString());
label1.Text = e.ProgressPercentage.ToString() + "%";
//throw new NotImplementedException();
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void btnGetDownload_Click(object sender, EventArgs e)
{
//First Download
InitiateDownload(URL, path + "name you give.txt", wc_DownloadFileCompleted, "name you give.txt");
//Second Download
InitiateDownload(URL, path + "name you give2.txt", wc_DownloadFileCompleted, "name you give2.txt");
}
}
}
When I download multiple files it downloads all at the same time and from time to time I get one or two downloads that become corrupted. Also when I have more than 10 or 15 my application freezes a bit because its downloading all at the same. I want to be able to download at at least one or two at a time. I have looked around in using async and await but had no luck with. In addition I want to put a progressbar for each download file. So basically a loop but inserted into a listview but do not know how to go about it or maybe how to approach it.

Can you check http://blogs.msdn.com/b/spike/archive/2013/06/12/how-to-download-multiple-files-concurrently-using-webclient-and-the-downloadfileasync-method.aspx.
As I understand you should configure simultaneous outgoing connection limit to a higher number.
In the App.config file for the project, add the maxconnection setting:
<?xmlversion="1.0"encoding="utf-8" ?>
<configuration>
<system.net>
<connectionManagement>
<addaddress = "*"maxconnection = "10" />
</connectionManagement>
</system.net>
</configuration>
Credits to upper link. But this can only explain freezes when large number of files requested. For file corruption I think another point needs to be solved.

WebClient multi file Downloader error

im using the following code to download 50+ files from my webserver
private void button5_Click(object sender, EventArgs e)
{
WebClient client = new WebClient();
client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(client_DownloadProgressChanged);
client.DownloadFileCompleted += new AsyncCompletedEventHandler(client_DownloadFileCompleted);
//downloads
client.DownloadFileAsync(new Uri("http://www.site.com/file/loc.file"), #"c:\app\loc ");
client.DownloadFileAsync(new Uri("http://www.site.com/file/loc.file"), #"c:\app\loc ");
client.DownloadFileAsync(new Uri("http://www.site.com/file/loc.file"), #"c:\app\loc ");
}
void client_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
double bytesIn = double.Parse(e.BytesReceived.ToString());
double totalBytes = double.Parse(e.TotalBytesToReceive.ToString());
double percentage = bytesIn / totalBytes * 100;
progressBar.Value = int.Parse(Math.Truncate(percentage).ToString());
}
private void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
{
MessageBox.Show("Game Update Finished!");
}
im wanting to download 1 file at a time with a continuing progress bar iv got most of the coding done but when i hit the "Download" button i get the following error
WebClient does not support concurrent I/O operations.
what do i need to do?

Feel the difference:
It CAN download multiple files in parallel manner (by one stream per
one file).
But it CAN'T download one file using multiple streams.
Here is example (MainWindow contain one button 'Start' and five progress bars):
public partial class MainWindow : Window
{
private WebClient _webClient;
private ProgressBar[] _progressBars;
private int _index = 0;
public MainWindow()
{
InitializeComponent();
_progressBars = new [] {progressBar1, progressBar2, progressBar3, progressBar4, progressBar5};
ServicePointManager.DefaultConnectionLimit = 5;
}
private void button1_Click(object sender, RoutedEventArgs e)
{
Interlocked.Increment(ref _index);
if (_index > _progressBars.Length)
return;
_webClient = new WebClient();
_webClient.DownloadProgressChanged += WebClient_DownloadProgressChanged;
_webClient.DownloadFileCompleted += WebClient_DownloadFileCompleted;
_webClient.DownloadFileAsync(new Uri("http://download.thinkbroadband.com/5MB.zip"),
System.IO.Path.GetTempFileName(),
_index);
}
private void WebClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs args)
{
var index = (int) args.UserState;
_progressBars[index-1].Value = args.ProgressPercentage;
}
private void WebClient_DownloadFileCompleted(object sender, AsyncCompletedEventArgs args)
{
var index = (int)args.UserState;
MessageBox.Show(args.Error == null
? string.Format("Download #{0} completed!", index)
: string.Format("Download #{0} error!\n\n{1}", index, args.Error));
}
}

you are running multiple downloads in parallel with the same WebClient instance - the error tells you that this is NOT supported - you either:
use multiple instances of WebClient (one per parallel download)
OR
download one file after the other
Relevant information:
http://msdn.microsoft.com/en-us/library/system.net.webclient.aspx
http://msdn.microsoft.com/en-us/magazine/cc700359.aspx

WebClient does not support concurrent I/O operations (multiple downloads) per instance, so you need to create a separate WebClient instance for each download. You can still perform each download asynchronously and use the same event handlers.

Trouble with WebClient.DownloadDataAsync(). Not downloading the data?

public string[] SearchForMovie(string SearchParameter)
{
WebClientX.DownloadDataCompleted += new
DownloadDataCompletedEventHandler(WebClientX_DownloadDataCompleted);
WebClientX.DownloadDataAsync(new Uri(
"http://www.imdb.com/find?s=all&q=ironman+&x=0&y=0"));
string sitesearchSource = Encoding.ASCII.GetString(Buffer);
}
void WebClientX_DownloadDataCompleted(object sender,
DownloadDataCompletedEventArgs e)
{
Buffer = e.Result;
throw new NotImplementedException();
}
I get this exception:
The matrix cannot be null. Refering to my byte[] variable Buffer.
So, I can conclude that the DownloadDataAsync isn't really downloading anything. What is causing this problem?
PS. How can I easily format my code so it appear properly indented here. Why can't I just copy past the code from Visual C# express and maintain the indentation here? Thanks! :D

The key word here is "async"; when you call DownloadDataAsync, it only starts the download; it isn't complete yet. You need to process the data in the callback (WebClientX_DownloadDataCompleted).
public string[] SearchForMovie(string SearchParameter)
{
WebClientX.DownloadDataCompleted += WebClientX_DownloadDataCompleted;
WebClientX.DownloadDataAsync(new Uri(uri));
}
void WebClientX_DownloadDataCompleted(object sender,
DownloadDataCompletedEventArgs e)
{
Buffer = e.Result;
string sitesearchSource = Encoding.ASCII.GetString(Buffer);
}
Also - don't assume ASCII; WebClientX.Encoding would be better; or just DownloadStringAsync:
static void Main()
{
var client = new WebClient();
client.DownloadStringCompleted += DownloadStringCompleted;
client.DownloadStringAsync(new Uri("http://google.com"));
Console.ReadLine();
}
static void DownloadStringCompleted(object sender,
DownloadStringCompletedEventArgs e)
{
if (e.Error == null && !e.Cancelled)
{
Console.WriteLine(e.Result);
}
}

why my WebClient upload file code hangs?

I am using VSTS 2008 + C# + .Net 3.5 + ASP.Net + IIS 7.0 to develop a Windows Forms application at client side to upload a file, and at server side I receive this file using an aspx file.
I find my client side application will hang after click the button to trigger upload event. Any ideas what is wrong and how to solve? Thanks!
Client side code,
public partial class Form1 : Form
{
private static WebClient client = new WebClient();
private static ManualResetEvent uploadLock = new ManualResetEvent(false);
private static void Upload()
{
try
{
Uri uri = new Uri("http://localhost/Default2.aspx");
String filename = #"C:\Test\1.dat";
client.Headers.Add("UserAgent", "TestAgent");
client.UploadProgressChanged += new UploadProgressChangedEventHandler(UploadProgressCallback);
client.UploadFileCompleted += new UploadFileCompletedEventHandler(UploadFileCompleteCallback);
client.UploadFileAsync(uri, "POST", filename);
uploadLock.WaitOne();
}
catch (Exception e)
{
Console.WriteLine(e.StackTrace.ToString());
}
}
public static void UploadFileCompleteCallback(object sender, UploadFileCompletedEventArgs e)
{
Console.WriteLine("Completed! ");
uploadLock.Set();
}
private static void UploadProgressCallback(object sender, UploadProgressChangedEventArgs e)
{
Console.WriteLine("{0} uploaded {1} of {2} bytes. {3} % complete...",
(string)e.UserState,
e.BytesSent,
e.TotalBytesToSend,
e.ProgressPercentage);
// Console.WriteLine (e.ProgressPercentage);
}
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Upload();
}
}
Server side code:
protected void Page_Load(object sender, EventArgs e)
{
string agent = HttpContext.Current.Request.Headers["UserAgent"];
using (FileStream file = new FileStream(#"C:\Test\Agent.txt", FileMode.Append, FileAccess.Write))
{
byte[] buf = Encoding.UTF8.GetBytes(agent);
file.Write(buf, 0, buf.Length);
}
foreach (string f in Request.Files.AllKeys)
{
HttpPostedFile file = Request.Files[f];
file.SaveAs("C:\\Test\\UploadFile.dat");
}
}

you are waiting in the main windows events thread, so your GUI will be frozen.
Try this (using non static methods allows you to use the Control.Invoke method to run callbacks on the windows GUI thread and free this thread in order to redraw)
public partial class Form1 : Form
{
private static WebClient client = new WebClient();
private static ManualResetEvent uploadLock = new ManualResetEvent(false);
private void Upload()
{
try
{
Cursor=Cursors.Wait;
Uri uri = new Uri("http://localhost/Default2.aspx");
String filename = #"C:\Test\1.dat";
client.Headers.Add("UserAgent", "TestAgent");
client.UploadProgressChanged += new UploadProgressChangedEventHandler(UploadProgressCallback);
client.UploadFileCompleted += new UploadFileCompletedEventHandler(UploadFileCompleteCallback);
client.UploadFileAsync(uri, "POST", filename);
}
catch (Exception e)
{
Console.WriteLine(e.StackTrace.ToString());
this.Cursor=Cursors.Default;
this.Enabled=false;
}
}
public void UploadFileCompleteCallback(object sender, UploadFileCompletedEventArgs e)
{
// this callback will be invoked by the async upload handler on a ThreadPool thread, so we cannot touch anything GUI-related. For this we have to switch to the GUI thread using control.BeginInvoke
if(this.InvokeRequired)
{
// so this is called in the main GUI thread
this.BeginInvoke(new UploadFileCompletedEventHandler(UploadFileCompleteCallback); // beginInvoke frees up the threadpool thread faster. Invoke would wait for completion of the callback before returning.
}
else
{
Cursor=Cursors.Default;
this.enabled=true;
MessageBox.Show(this,"Upload done","Done");
}
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Upload();
}
}
}
And do the same thing in your progress (you could update a progressbar indicator for example).
Cheers,
Florian