Question

I’m using the Silverlight business application (Navigation application) template that comes with Visual studio 2010. I have 3 pages in my app ..Home, About and Contact.

Now my requirement is that, based on a certain configuration setting stored in the web.config file, retrieved via an async WCF call, I need to do 2 things via code behind
1. Add HyperLinks to the one or more of the above pages
2. And also make the content frame in the MainPage.Xaml to load a particular page by default

My MainPage.Xaml looks like following

<UserControl xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"
         x:Class="MainPage"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

            <StackPanel x:Name="LinksStackPanel"
                        Style="{StaticResource LinksStackPanelStyle}">
            </StackPanel>

            <navigation:Frame x:Name="ContentFrame"
                              Navigated="ContentFrame_Navigated"
                              NavigationFailed="ContentFrame_NavigationFailed">
                <navigation:Frame.UriMapper>
                    <uriMapper:UriMapper>
                        <uriMapper:UriMapping Uri=""
                                              MappedUri="/Views/Home.xaml" />
                        <uriMapper:UriMapping Uri="/{pageName}"
                                              MappedUri="/Views/{pageName}.xaml" />
                        <uriMapper:UriMapping MappedUri="/Views/{pageName}.xaml"
                                              Uri="{}{pageName}" />
                    </uriMapper:UriMapper>
                </navigation:Frame.UriMapper>
            </navigation:Frame>

In my code behind of MainPage.xaml.cs I do the following

    /// <summary>
    /// Default constructor
    /// </summary>
    public MainPage()
    {
        InitializeComponent();
        Loaded += new RoutedEventHandler(MainPage_Loaded);
    }

    void MainPage_Loaded(object sender, RoutedEventArgs e)
    {
        // Determine if deployed in TEST or PROD
        Client.IsTestCompleted += new EventHandler<IsTestCompletedEventArgs>(Client_IsTestCompleted);
        client.IsTestAsync();
    }

    void Client_IsTestCompleted(object sender, IsTestCompletedEventArgs e)
    {
        MainPage.IsTest = e.Result;

        if (MainPage.IsTest)
        {
            // Add hyperling to About page
            this.AddHyperLink("About", "about");

            // load about.xaml in the content frame
            this.ContentFrame.Source = new Uri("About", UriKind.Relative);
        }
        else
        {
            // Add hyperlinks to Home, contact and About page
            this.AddHyperLink("Home", "home");
            this.AddHyperLink("Contact", "contact");
            this.AddHyperLink("About", "about");


            // load about.xaml in the content frame
            this.ContentFrame.Source = new Uri("About", UriKind.Relative);
        }
    }

    private void AddHyperLink(string uri, string content)
    {
        HyperlinkButton hb = new HyperlinkButton();
        hb.NavigateUri = new Uri(uri, UriKind.RelativeOrAbsolute);
        hb.TargetName = "ContentFrame";
        hb.Content = content;
        hb.Style = Application.Current.Resources["LinkStyle"] as Style;
        this.LinksStackPanel.Children.Add(hb);
    }

So this working as expected. That is when I start the application it loads the about page only when deployed in test and when deployed in prod shows 3 links with content frame navigated to about page.

But the problem is, the constructor of the HomePage, Home_Loaded and OnNavigatedTo() are getting called from somewhere before the similar methods in AboutPage are called.

This is wasting a lot of time bcoz, it unnecessarily execute the code in these methods when its not being loaded in the frame

This is code in Home.Xaml.cs

public Home()
    {
        InitializeComponent();
        Loaded += new RoutedEventHandler(Home_Loaded);
    }

    /// <summary>
    /// Load the home page
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    void Home_Loaded(object sender, RoutedEventArgs e)
    {
      //Expensive code
    }

    /// <summary>
    /// Executes when the user navigates to this page.
    /// </summary>
    /// <param name="e"></param>
    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
       //Expensive code
    }

So my questions are…

1. Who is calling these methods in HomePage and why? Since I was loading about.xaml in the content frame I dont expect any code in HomePage to execute but only the code in About.xaml

2. And what do i need to do to make sure that these methods in the HomePage are not executed on application load but only when navigated to that page by clicking on “Home” link.

3. Is there a better way to achieve this navigation problem , other than setting the source of the content frame

Thanks for the help

Answer 1

I did what Rikkos suggested. Changed the Uri mapping of default page to an empty page and it works like a charm now

<uriMapper:UriMapper>
                    <uriMapper:UriMapping Uri=""
                                          MappedUri="/Views/EmptyPage.xaml" />