Connect to XML file at web address for WP7 app

Question

I've been trying to learn the ins-and-outs of Windows Phone 7 programming over the past few weeks. I have learned most of the basics but I've been having trouble finding a tutorial explaining exactly how to do something with XML. I want to create a very basic app which accesses an XML file at a web address and displays the various items within the file as text within the app. I've come across several tutorials which all seem to do it in a different way, or aren't explaining exactly the thing it is I want to do. I don't want to search the XML file, I don't want to update it, I just want to retrieve it's contents. Within the XML file are "items" and within those are categories like "title" and "description". I want the app to list all of the items and within each one display it's title and description.

To be more specific I know that I bind the contents to textblocks using {Binding Title} or {Binding Description}. I'm just not sure how to connect to the file using WebClient or whatever the easiest method is. I have no problem displaying the contents of an offline XML file that is already in my solution explorer.

I'm sure there is a very simple way to do this, and I really appreciate all of your help.

Answer 1

ScottGu created an app which demonstrates what you need. (Code below is very similar as couldn't find link to source from his example.)

The app retrieves XML from a web service (in this case from Twitter.)

    private void GetTweets()
    {
        WebClient twtr = new WebClient();

        twtr.DownloadStringCompleted += new DownloadStringCompletedEventHandler(twitter_DownloadStringCompleted);
        twtr.DownloadStringAsync(new Uri("http://search.twitter.com/search.atom?&q=searchterm"));
    }

It then parses the XML into a collection of object.

    void twitter_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
    {
        if (e.Error != null)
            return;

        XElement xmlTweets = XElement.Parse(e.Result);

        var list = new List<TweetViewModel>();

        foreach (XElement t in xmlTweets.Elements("{http://www.w3.org/2005/Atom}entry"))
        {
            var userName = t.Element("{http://www.w3.org/2005/Atom}author").Element("{http://www.w3.org/2005/Atom}name").Value.Split(' ')[0];
            var message = t.Element("{http://www.w3.org/2005/Atom}title").Value;
            var imageSource = (from t2 in t.Elements("{http://www.w3.org/2005/Atom}link")
                               where t2.Attribute("type").Value.Contains("image")
                               select t2.Attribute("href").Value).First();

            list.Add(new TweetViewModel
                    {
                        UserName = userName,
                        Message = message,
                        ImageSource = imageSource
                    });
        }

        twitterList.ItemsSource = list;
    }


public class TweetViewModel
{
    public string UserName { get; set; }
    public string Message { get; set; }
    public string ImageSource { get; set; }
}

This is then bound to a list.

<ListBox HorizontalAlignment="Left" Name="twitterList" VerticalAlignment="Top" Width="476">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal" Height="132">
                <Image Source="{Binding ImageSource}" Height="73" Width="73" VerticalAlignment="Top" Margin="0,10,8,0"/>
                <StackPanel Width="370">
                    <TextBlock Text="{Binding UserName}" Foreground="#FFC8AB14" FontSize="28" />
                    <TextBlock Text="{Binding Message}" TextWrapping="Wrap" FontSize="24" />
                </StackPanel>
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

It was written with the first CTP of the tools/SDK but hopefully it should still be simple enough to get this working.

Answer 2

UPDATE:

I think you were right that the problem may be when I call GetRoster. This is the context in which I'm calling it:

'

namespace TwitterMix
{
public partial class MainPage : PhoneApplicationPage
{
    // Constructor
    public MainPage()
    {
        InitializeComponent();
    }


    private void GetRoster()
    {
        WebClient rstr = new WebClient();

        rstr.DownloadStringCompleted += new DownloadStringCompletedEventHandler(roster_DownloadStringCompleted);
        rstr.DownloadStringAsync(new Uri("http://www.danfess.com/data.xml"));
    }

'

What would be the correct place in which to call it? By the way I'm sorry about the code sections not appearing correctly.

---

Hey guys! Thanks for the help! I didn't create an account earlier so this is probably going to show up as an answer since I'm on a different computer. I did my best in changing that Twitter Tutorial into what I am trying to do. I'm getting no errors but it's not showing any content within the emulator. I created an XML file and uploaded it to my personal website. Unfortunately, I cannot get the code sample button to work even remotely well. So I'm sorry this looks so poorly. The XML file contained this info:

<?xml version="1.0" encoding="utf-8" ?>
<roster>
  <person><name>Blake</name><age>25</age></person>
  <person><name>Jane</name><age>29</age></person>
  <person><name>Bryce</name><age>29</age></person>
  <person><name>Colin</name><age>29</age></person>
</roster>

Here is MainPage.xaml.cs:

private void GetRoster()
    {
        WebClient rstr = new WebClient();

        rstr.DownloadStringCompleted += new DownloadStringCompletedEventHandler(roster_DownloadStringCompleted);
        rstr.DownloadStringAsync(new Uri("http://www.MyPersonalWebsiteURL.com/data.xml"));
    }

    void roster_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
    {
        if (e.Error != null)
            return;

        XElement xmlPersons = XElement.Parse(e.Result);

        var list = new List<RosterViewModel>();

        foreach (XElement person in xmlPersons.Elements("person"))
        {
            var name = person.Element("name").Value;
            var age = person.Element("age").Value;


            list.Add(new RosterViewModel
            {
                Name = name,
                Age = age,
             });
        }

        rosterList.ItemsSource = list;
    }


    public class RosterViewModel
    {
        public string Name { get; set; }
        public string Age { get; set; }
    }
}

Now MainPage.xaml:

'

<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>

    <!--TitlePanel contains the name of the application and page title-->
    <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">
        <TextBlock x:Name="ApplicationTitle" Text="MY APPLICATION" Style="{StaticResource PhoneTextNormalStyle}"/>
        <TextBlock x:Name="PageTitle" Text="page name" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
    </StackPanel>

    <!--ContentPanel - place additional content here-->
    <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
        <ListBox HorizontalAlignment="Left" Name="rosterList" ItemsSource="rosterList" VerticalAlignment="Top" Width="476">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Horizontal" Height="132">

                        <StackPanel Width="370">
                            <TextBlock Text="{Binding Name}" Foreground="#FFC8AB14" FontSize="28" />
                            <TextBlock Text="{Binding Age}" TextWrapping="Wrap" FontSize="24" />
                        </StackPanel>
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>
</Grid>

'

However! When I run the app in the emulator I receive no errors, but no content is displayed whatsoever. I know the solution is probably very simple so I'd like to reiterate how much your help means to me. Thanks very much for any advice you can provide.