Use webClient.DownloadFileAsync to download and save file without clicking button

Question

I'm writing a C# Win-forms application that I want to programmatically download and save a file to a client computer without user intervention.

I've found several suggestions, such as this one on stackoverflow: How to download a file from a website in C#

I tried using the webClient.DownloadFileAsync method as well as a suggestion found at csharp-examples http://www.csharp-examples.net/download-files/ Download File Asynchronously

If I plug the URL into either Firefox or IE directly, the desired file appears in a dialog box where I would need to either click Open or Save. I want to be able to pull the file down and save it without the user having to click any buttons.

While testing this in a WinForm, I do have a button click event. The problem I'm encountering is that, if I use the webClient.DownloadFileAsync examples, no file is downloaded. I also added DownloadFileCompleted and DownloadProgressChanged event handlers and a progressBar1 to the form.

I added a MessageBox to the webClient_DownloadFileCompleted, and the message displays instantly but no file has been downloaded. I've included 2-samples of what I've tried so far below. I have the using statements for System.Net, System.IO and System.Diagnostics;

Using the webClient.DownloadFileAsync, is there a way to download and save the file without having the user click a button? Thanks.

The first example I've tried:

private void btnDownload_Click(object sender, EventArgs e)
{
    WebClient webClient = new WebClient();
    webClient.DownloadFileCompleted += new     AsyncCompletedEventHandler(webClient_DownloadFileCompleted);
    webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler

(webClient_DownloadProgressChanged);
    webClient.DownloadFileAsync(new Uri("http://download.my.org/files/media/myFile.pdf"), @"C:
    \mySaveLocation\");
}

The 2nd example I've tried:

public void DownloadFile(string urlAddress, string location)
{
    using (webClient = new WebClient())
    {
        webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed);
        webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(ProgressChanged);

        //The variable that will be holding the url address (making sure it starts with http://)
        Uri URL = urlAddress.StartsWith("http://", StringComparison.OrdinalIgnoreCase) ? new
          Uri(urlAddress) : new Uri("http://" + urlAddress);

        try
        {
            //Start downloading the file
            webClient.DownloadFileAsync(URL, location);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }
}

I even tried calling this latter method in the click event and passing in the parameters for the URL and saving location, but still no file downloaded.

I like the 2nd example, because I can pass in a different URL and saving location for different files.

Would someone please suggest how I might use the webClient code to both download AND save the file, but without the user having to interact with a dialog? Once the file downloads, I'm working with it behind the scenes to accomplish things. Thanks.

score 0 · Answer 1 · answered Oct 03 '14 at 23:27

0

Try capturing download requests with Fiddler: http://www.telerik.com/fiddler

See if request/response is different when you manually download file and when you download it in your app.

answered Oct 03 '14 at 23:27

Sergey Volegov

890
1
7
15

I reconfigured my code to use a simpler syntax and it works fine. private void btnDownload_Click(object sender, EventArgs e) { WebClient webClient = new WebClient(); webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed); webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(ProgressChanged); webClient.Headers.Set(HttpRequestHeader.ContentType, "application/octet-stream"); webClient.DownloadFileAsync(new Uri("http://thedownloadsite.anywhere.org/files/MyBook.pdf"), @"C:\MySaveLocation\MyBook.pdf"); } – CodeMann Oct 08 '14 at 19:48

Use webClient.DownloadFileAsync to download and save file without clicking button

1 Answers1