Portable Class Libraries with WP7 support in Visual Studio 2013 (RC)

Note: This is my personal blog. Although I did an internship at Microsoft and this post is about a product made by Microsoft, I figured out the info in this blog post after the internship in my own time without any help. The "hack" described in this blog post, leaves Visual Studio 2013 RC in an unsupported state. Perform it at your own risk.

Update 10/17/2013: It looks like this trick still works for the final release of Visual Studio 2013. Use it at your own risk.

With the recent release of Visual Studio 2013 RC and the Windows 8.1 RTM for MSDN subscribers, I started upgrading some of my code to work with Windows 8.1. Part of this code resided in a Portable Class Library (PCL) that also targets Windows Phone 7.5 (and therefore Silverlight 4) next to Windows Phone 8, Windows 8 and .NET 4.5. Visual Studio 2013 has dropped support for some older platforms including Windows Phone 7.5, Silverlight 4 and older.

Since you can install Visual Studio 2012 and 2013 side by side, you can still continue building Windows Phone 7 apps in 2012 if needed. Problems occur as soon as you want to use a PCL for Windows 8.1 development that also targets Windows Phone 7. Several others also came accross this issue. When opening such a PCL in Visual Studio 2013, it will upgrade the project to Windows Phone 8, Windows 8 and .NET 4.5 as in the picture below and breaks the compatibility with Windows Phone 7 in Visual Studio 2012.

Visual Studio 2013 will upgrade the project.

While I was investigating if I could work around this issue, I found that all the portable profiles are actually there on disk in the C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETPortable folder, when you install Visual Studio 2013, including those with support for Windows Phone 7 and Silverlight 4. As Daniel Plaisted pointed out on Twitter, this is because different versions of Visual Studio share the portable profiles.

Folder containing the portable profiles.

I was wondering why Visual Studio would upgrade the project while the profile was there on disk. While digging through the xml files for Profile104 (C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETPortable\v4.0\Profile\Profile104\), which is the profile I was using, I found some xml files in the SupportedFrameworks subfolder. These xml files defined a MinimumVisualStudioVersion and a MaximumVisualStudioVersion. For Profile104, one of the files contained MaximumVisualStudioVersion="11" which means Visual Studio 2012. Changing all xml files for the profile to have MaximumVisualStudioVersion="12", which means Visual Studio 2013, made my scenario work after a restart of Visual Studio. I can now open the PCL in Visual Studio 2013 without it being upgraded. Make sure you restart VS after this change to make it work.

Xml file that defines the minimum and maximum Visual Studio versions

Note that changing these xml files is unsupported and leaves you in an unsupported state. It might decrease the stability of Visual Studio 2013 RC, although I did not find any issues with this yet, but that does not mean there are none. Make these changes at your own risk and only for the profiles you really need!

Hope this helps for everyone who still needs to do Windows Phone 7.5 development. If you want support for Windows Phone 7 in Visual Studio 2013, please let the team know via their uservoice site.

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The case of the not working Youtube app on Windows Phone 8

Somewhere in November I received my new Windows Phone 8 device, the Lumia 920. I do not often watch youtube videos on my phone, but when I tried to play a movie, the Phone asked me if I wanted to search for an app in the store.


There is a youtube app for Windows Phone that allows you to play movies, which is basically just a wrapper around the mobile youtube site since Google is actively blocking Windows Phone access to the youtube api. Although I had that app already installed, it still asked me to look in the store. When I chose "yes" there were actually no apps found.


It turns out that the mobile youtube site is not working on Windows Phone if you set your Website preference to "desktop version" instead of  "mobile version". Why this happens is unclear to me but if you have this problem you could check if you might have it set to  "desktop version". Changing it to "mobile version" fixes the problem and you can play videos fine.

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Fixing the LongListSelector part 2: Making the SelectedItem bindable.

One of the problems of the LongListSelector in the current release of the Silverlight for Windows Phone Toolkit comes to the surface in MVVM scenarios. You often bind the SelectedItem to some property on the viewmodel so you can have access to the selected item. This works fine for a ListBox, but on the LongListSelector it doesn't work.

The problem is that the SelectedItem property on the LongListSelector is not a dependency property, and is therefore not bindable. The solution to this problem is of course to change it to a dependency property. But if you don't want to change the source and recompile there is also another way to add this.

The following piece of code creates a new control which inherits from the normal LongListSelector.

- It adds a new dependency property called SelectedItem and hides the SelectedItem property of the base class by using the "new" modifier.

- It explicitly sets the SelectedItem dependency property when the selection changes, which in fact comes down to syncing the dependency property with the  SelectedItem property of  the base class.

 public class LongListSelector : Microsoft.Phone.Controls.LongListSelector
    public LongListSelector()
        SelectionChanged += LongListSelector_SelectionChanged;

    void LongListSelector_SelectionChanged(object sender, SelectionChangedEventArgs e)
        SelectedItem = base.SelectedItem;

    public static readonly DependencyProperty SelectedItemProperty =
            new PropertyMetadata(null, OnSelectedItemChanged)

    private static void OnSelectedItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        var selector = (LongListSelector)d;
        selector.SelectedItem = e.NewValue;

    public new object SelectedItem
        get { return GetValue(SelectedItemProperty); }
        set { SetValue(SelectedItemProperty, value); }

If you are going to recompile the toolkit, than don't forget to get the latest sources from codeplex. There are some new fixes checked in in the past few days.

If you have any question regarding this blog post or another related thing, feel free to contact me via the comments, the contact form or twitter.

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Fixing the LongListSelector part 1: Recompile the source.

Today I came across an issue with the LongListSelector, part of the Silverlight for Windows Phone Toolkit. Solving the issue seemed pretty simple in the end, but first some background.

The LongListSelector is a control that can be used to create a list of groups. A good example of this is the contacts list in the people hub. In that list the contacts are organized based on the first letter of their name. Every group contains a header, in this case the first letter, and using this header you can very easily switch between groups. By using the LongListSelector from the toolkit, developers can create the same experiences in their apps.

The issue I encountered was the fact that I was getting ArgumentOutOfRange exceptions when an item was added to a group dynamically. This issue was supposed to be fixed in the November 2011 release, as stated in the release notes:

LongListSelector bug fixes around OutOfRange exceptions, wrong ordering of items, grouping issues, and scrolling events. ItemTuple is now refactored to be the public type LongListSelectorItem to provide users better access to the values in selection changed handlers.

Well this doesn't seem to be the case exactly. Most of those fixes were actually in changeset 71191 and 71199, which according to the codeplex site are included in the November release. This appears to be not so. When comparing some of the code in the installed Microsoft.Phone.Controls.Toolkit.dll to the source on codeplex it seems to be the case that the installed dll is compiled from a revision at least before 70993.

The solution is simple:

- Download the latest source from codeplex (this currently also includes some fixes to the PhoneTextBox, changeset 74775).

- Compile it.

- Use the resulting dll instead of the one installed by the toolkit.

Happy coding!

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FontSize and pixel height in Silverlight for Windows Phone

Recently I came accross the issue where I wanted to limit the number of lines shown in my TextBlock on Windows Phone to for example 3. If the text was longer than 3 lines, the rest of the text should just not be shown. To do this I wanted to set the height of the TextBlock to a fixed height, to be exact 3 times the height of one line. This seems trivial, but to find the height of a line, you need to know something about the way Silverlight measures and calculates heights.

In Silverlight on the desktop and Silverlight for Windows Phone the measuring system is based on pixel units instead of Device Independent Pixel (DIP) units, as it is in WPF. Also the measuring system does not support unit measure string suffixes such as pt, cm or px. Silverlight measurements are always pixel units.

So if we specify the height of a Grid or a TextBlock to be 30 it actually is 30 pixel units. FontSize is no exception to this rule so when you specify 30 as the FontSize, you get a font that from the top of its ascenders to the bottom of its descenders measures approximately 36 pixels. Nevertheless the height of the corresonding TextBlock will be higher, because additional space is used to preserve space between successive lines. This concept is called leading.

In classical typography font sizes are expressed in units of points where a point is almost 1/72th of an inch. Digital typography assumes almost always a value of exactly 1/72th of an inch. This means that text with a font size of 72 points measures approximately 1 inch. Converting between pixels and points is difficult because it depends on the device you are using. Using a printer with 600 dpi (dots per inch) a font with size 72 will measure 600 pixels.

Windows assumes video displayes to have a dpi of 96. Using this assumption one can easily transform pixels into points and the other way around using the following two formulas:

points = 72/96 * pixels = 3/4 * pixels
pixels = 96/72 * points = 4/3 * points

Although Windows Phone screens have a much higher dpi than 96 these formulas also work for the phone. Suppose you want to set a 45 point font. Then you need to set the FontSize property to 60. On top of this Silverlight will add leading, which is approximately 33% of the size set as FontSize, which will result in the height of the TextBlock being 80 pixels.

It is possible to change this behavior by using the LineHeight and LineStackingStrategy properties of a TextBlock. You can read more about it here.

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How to override theme resources in Windows Phone 7.5 (Mango)

Windows Phone 7 standard comes with some predefined themes and accent colors the user can choose of. You can read more about them here. This enables aaplications to automatically get adjusted to the users theme which makes the experience for user a lot better, because applications can adjust to the user's preferences. But sometimes this is not what you as a developer want. When you are for example building a facebook application you probably want the app to use the colors facebook uses, but you can of course have your own reason to not have your app always adjust to the current theme.

Windows Phone Themes

The different themes Windows Phone 7 comes with are included in the SDK and can be found in C:\Program Files (x86)\Microsoft SDKs\Windows Phone\v7.0\Design on 64-bit windows installations and in C:\Program Files\Microsoft SDKs\Windows Phone\v7.0\Design on 32-bit installations. Each theme consists of a System.Windows.xaml file which defines the styles for the controls and a ThemeResources.xaml file which defines theme colors, brushes and text styles.

Overriding themes on Windows Phone 7.0

On Windows Phone 7.0 overriding the theme on the phone was quite easy and was well explained here and here. The technique comes down to defining a custom ResourceDictionary and add this ResourceDictionary to the Resources section in the app.xaml file.

<Application x:Class="ThemedApplication.App"

    <!--Application Resources-->
        <ResourceDictionary x:Key="styles">
                <ResourceDictionary Source="Themes/styles.xaml"/>

    <!--Required object that handles lifetime events for the application-->
        Launching="Application_Launching" Closing="Application_Closing" 
        Activated="Application_Activated" Deactivated="Application_Deactivated"/>


This resource dictionary can then be used to override theme resources, for example the PhoneBackgroundColor and PhoneBackgroundBrush can be defined to be always white in your application as shown below.


	<!-- 100 percent White-->
	<Color x:Key="PhoneBackgroundColor">#FFFFFFFF</Color>

	<SolidColorBrush x:Key="PhoneBackgroundBrush" Color="{StaticResource PhoneBackgroundColor}"/>

An example solution is attached at the bottom of this post.

Overriding themes in Windows Phone 7.5 (Mango)

When using the above overriding in a Windows Phone Mango application the technique does not work anymore. The reason behind this probably has to do with the switch between the silverlight 3 runtime and the silverlight 4 runtime which added support for implicit syles and a lot of other xaml changes. In a thread on the App Hub forums, about this technique not working anymore, Peter Torr, Program Manager in the Windows Phone 7 Application Platform team, explained that this was actually a bug in Silverlight on Windows Phone 7.0 and that this is "fixed" in Mango. He also gives two work-arounds you can use in Mango.

The first is the use of implicit styles which is a feature of silverlight 4 that now comes with mango. The problem with this approach is that you have to override the style for all controls to get them use the theme overrides. If you only want to change some colors this option costs a lot more work than before.

The second option is a lot better to implement if you just want to change some theme colors, although it is not as beautiful as simply including an extra resource dictionary. It works by changing the built-in styles instead of overriding them. This changing of styles can be done in the following way.

(App.Current.Resources["PhoneBackgroundBrush"] as SolidColorBrush).Color = Colors.White;

Another advantage of this technique over implicit styles is that this should also works on Windows Phone 7.0 although I did not test that. A disadvantage is that there is no design-time support when using this technique. One question that comes up is were to place these overrides. I found out by experience that the most useful place to put this overrides is after the InitializeComponent() method call in app.xaml.cs as shown below.

public partial class App : Application
        /// <summary>
        /// Provides easy access to the root frame of the Phone Application.
        /// </summary>
        /// <returns>The root frame of the Phone Application.</returns>
        public PhoneApplicationFrame RootFrame { get; private set; }

        /// <summary>
        /// Constructor for the Application object.
        /// </summary>
        public App()
            // Global handler for uncaught exceptions. 
            UnhandledException += Application_UnhandledException;

            // Standard Silverlight initialization

            // Change default styles

            // Phone-specific initialization

            // Show graphics profiling information while debugging.
            if (System.Diagnostics.Debugger.IsAttached)
                // Display the current frame rate counters.
                Application.Current.Host.Settings.EnableFrameRateCounter = true;

                // Show the areas of the app that are being redrawn in each frame.
                //Application.Current.Host.Settings.EnableRedrawRegions = true;

                // Enable non-production analysis visualization mode, 
                // which shows areas of a page that are handed off to GPU with a colored overlay.
                //Application.Current.Host.Settings.EnableCacheVisualization = true;

                // Disable the application idle detection by setting the UserIdleDetectionMode property of the
                // application's PhoneApplicationService object to Disabled.
                // Caution:- Use this under debug mode only. Application that disables user idle detection will continue to run
                // and consume battery power when the user is not using the phone.
                PhoneApplicationService.Current.UserIdleDetectionMode = IdleDetectionMode.Disabled;


        // Code to execute when the application is launching (eg, from Start)
        // This code will not execute when the application is reactivated
        private void Application_Launching(object sender, LaunchingEventArgs e)

        // Code to execute when the application is activated (brought to foreground)
        // This code will not execute when the application is first launched
        private void Application_Activated(object sender, ActivatedEventArgs e)

        // Code to execute when the application is deactivated (sent to background)
        // This code will not execute when the application is closing
        private void Application_Deactivated(object sender, DeactivatedEventArgs e)

        // Code to execute when the application is closing (eg, user hit Back)
        // This code will not execute when the application is deactivated
        private void Application_Closing(object sender, ClosingEventArgs e)

        // Code to execute if a navigation fails
        private void RootFrame_NavigationFailed(object sender, NavigationFailedEventArgs e)
            if (System.Diagnostics.Debugger.IsAttached)
                // A navigation has failed; break into the debugger

        // Code to execute on Unhandled Exceptions
        private void Application_UnhandledException(object sender, ApplicationUnhandledExceptionEventArgs e)
            if (System.Diagnostics.Debugger.IsAttached)
                // An unhandled exception has occurred; break into the debugger

        private void InitializeStyleChanges()
            //87 percent Black - #DE000000
            (App.Current.Resources["PhoneForegroundBrush"] as SolidColorBrush).Color = Color.FromArgb(0xDE, 0x0, 0x0, 0x0);
            //100 percent White - #FFFFFFFF
            (App.Current.Resources["PhoneBackgroundBrush"] as SolidColorBrush).Color = Colors.White;

        #region Phone application initialization

        // Avoid double-initialization
        private bool phoneApplicationInitialized = false;

        // Do not add any additional code to this method
        private void InitializePhoneApplication()
            if (phoneApplicationInitialized)

            // Create the frame but don't set it as RootVisual yet; this allows the splash
            // screen to remain active until the application is ready to render.
            RootFrame = new PhoneApplicationFrame();
            RootFrame.Navigated += CompleteInitializePhoneApplication;

            // Handle navigation failures
            RootFrame.NavigationFailed += RootFrame_NavigationFailed;

            // Ensure we don't initialize again
            phoneApplicationInitialized = true;

        // Do not add any additional code to this method
        private void CompleteInitializePhoneApplication(object sender, NavigationEventArgs e)
            // Set the root visual to allow the application to render
            if (RootVisual != RootFrame)
                RootVisual = RootFrame;

            // Remove this handler since it is no longer needed
            RootFrame.Navigated -= CompleteInitializePhoneApplication;


An example using this technique is also attached below. If you have any questions on this don't hesitate to ask them in the comments.



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