How to force WebClient to DownloadStringAsync every time on app launch

Question

I'm trying to write a RSS Reader that reads data from a remote XML file, the problem is that when I run application for the first time it downloads normally but when I update the information on XML file and run application again it does not download the new items. I call it on public Main()

WebClient wc = new WebClient();
wc.DownloadStringAsync(new Uri("http://suntvhost.do.am/sunnews.xml"));
wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);

Handler:

private void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
        {
            //This simple test will return an error if the device is not connected to the internet
            if (e.Error != null)
                return;
            XElement xmlitems = XElement.Parse(e.Result);
            // We need to create a list of the elements
            List<XElement> elements = xmlitems.Descendants("item").ToList();
            // Now we're putting the informations that we got in our ListBox in the XAML code
            // we have to use a foreach statment to be able to read all the elements 
            // Description 1 , Link1 , Title1 are the attributes in the RSSItem class that I've already added
            List<RSSItem> aux = new List<RSSItem>();
            foreach (XElement rssItem in elements)
            {
                RSSItem rss = new RSSItem();
                rss.Description1 = rssItem.Element("description").Value;
                rss.Link1 = rssItem.Element("link").Value;
                rss.Title1 = rssItem.Element("title").Value;
                rss.Date1 = rssItem.Element("pubDate").Value;
                aux.Add(rss);

                TextBlock tbTitle = new TextBlock();
                tbTitle.Text = "\n" + rss.Title1;
                ListBoxRss.Items.Add(tbTitle);
             // and so on for the rest of items...
            }
        }

score 3 · Accepted Answer · answered Jun 24 '14 at 08:33

3

If you get the same RSS file then this might be due to client side caching.
Forcing Windows Phone to download the RSS file worked for me by adding this HTTP-Header:

wc.Headers[ HttpRequestHeader.IfModifiedSince ] = "Sat, 29 Oct 1994 19:43:31 GMT";

answered Jun 24 '14 at 08:33

Volker Voecking

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Mikko Viitala · Answer 2 · 2014-06-25T18:45:20.030

1

All you have to do is the following:

string myUrl = "http://suntvhost.do.am/sunnews.xml?rand={0}";
...
_webClient.DownloadStringAsync(new Uri(string.Format(myUrl, DateTime.Now.Ticks)));

edited Jun 25 '14 at 18:45

answered Jun 24 '14 at 08:50

Mikko Viitala

8,344
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score 0 · Answer 3 · answered Jun 24 '14 at 08:25

I would start by registering the event handler before you actually try to get some results. It might be too late then already to register that event handler:

WebClient wc = new WebClient();
wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
wc.DownloadStringAsync(new Uri("http://suntvhost.do.am/sunnews.xml"));

Also, just returning when there is an error doesn't make it easy to diagnose any problems, to do something to write it to a log file, etc.

score 0 · Answer 4 · edited May 23 '17 at 11:56

0

The problem is that WebClient is caching the data.

More about that here: C# WebClient disable cache

edited May 23 '17 at 11:56

Community

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answered Jun 24 '14 at 08:32

klm_

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How to force WebClient to DownloadStringAsync every time on app launch

4 Answers4