pass data from viewmodel to code behind windows phone

Question

I was trying to use the MVVM pattern on my first (very simple) WP7 app but I got seriously stuck and now I am just trying to get it working without caring about MVVM.

I have a MainViewModel for my MainPage, which works fine. I have a button that passes some data and navigates to a "details page." I had setup a navigation service to navigate to the details page and pass parameters, which works fine. I just couldn't get the databinding to the view working. Since it is a simple app, I decided I would pass the data from the DetailsPageVieModel.cs to the DetailsPage.xaml.cs code behind and do the work there. Here is what that veiw model portion looks like.

public override void Initialize(IDictionary<string, string> parameters)
{
    DetailsPage dp = new DetailsPage();
    //DetailsPage dp = Application.Current.RootVisual as DetailsPage;
    base.Initialize(parameters);
    parameters.TryGetValue("url", out vidUrl);
    dp.LoadVideoData(vidUrl);
}

In my DetailsPage.xaml.cs I have the following:

    public void LoadVideoData(string url)
    {
        HtmlWeb doc = new HtmlWeb();
        doc.LoadAsync("http://mydomain.com/video.php?url=" + url);
        doc.LoadCompleted += doc_LoadCompleted;
    }

    private void doc_LoadCompleted(object sender, HtmlDocumentLoadCompleted e)
    {
        this.vidTitle.Text = e.Document.GetElementbyId("title").InnerText;
        vidId = e.Document.GetElementbyId("youtubeId").InnerText;
        this.vidUrl.Source = new Uri("http://mydomain.com/video.php?url=" + vidUrl, UriKind.Absolute);

        BitmapImage bi = new BitmapImage();

        using (IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication())
        {
            using (IsolatedStorageFileStream fileStream = myIsolatedStorage.OpenFile("temp.jpg", FileMode.Open, FileAccess.Read))
            {
                bi.SetSource(fileStream);
                this.vidImg.Height = bi.PixelHeight;
                this.vidImg.Width = bi.PixelWidth;
            }
        }
        this.vidImg.Source = bi;
    }

And here is the relevant DetailsPage.xaml code

<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
        <StackPanel>
            <TextBlock x:Name="vidTitle" Canvas.ZIndex="99" />
            <TextBlock Canvas.ZIndex="99" Text="Tap on the image to view the video." FontSize="14" Margin="0"/>
            <Button Margin="0 -50" Padding="0" BorderThickness="0">
                <Image x:Name="vidImg" Height="225" />
            </Button>
            <StackPanel Canvas.ZIndex="99" Height="516">
                <phone:WebBrowser x:Name="vidUrl" IsScriptEnabled="True" Height="516" Margin="0"/>
            </StackPanel>
        </StackPanel>
    </Grid>

I am guessing the problem lies with the following

DetailsPage dp = new DetailsPage();
//DetailsPage dp = Application.Current.RootVisual as DetailsPage;

Neither of these lines of code works. The first line executes properly but the page doesn't get updated with the proper data. And the second line gives me a runtime error message when it gets to the dp.LoadVideoData(vidUrl); line.

This is my first Windows Phone app and I would appreciate any help anyone can provide.

Kamal

Answer 1

After digging around some more, I found the following solution.

DetailsPage currentPage = (App.Current as App).RootFrame.Content as DetailsPage;

I put this code in DetailsPageViewModel.cs. But for other newbies like me, there is nothing special about the name of the file. It could have very well been Monkey.cs. The above code just gives you access to the code behind of the current page being displayed.