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  • A story of Murphy&ndash;my technical issues at TechDays Switzerland #chtd

    - by Laurent Bugnion
    I had two sessions at the recent Swiss TechDays. While the first one (Advanced Development for Windows Phone 8) went extremely well (I think), I had a very annoying technical issue in the beginning of my second session. First let me add that I talked to Microsoft about that and I hope they will change a few things in the room assignment for next year. My two sessions were one right after the other, with only 15 minutes break to change room. I don’t mind having two sessions so close from each other, but I would really like them to be in the same room in order to avoid having to move my laptops (plural, that will become important later) and redoing the tech check. That being said, I am guilty of not checking where my talks would be before the day before the conference, and when I did notice, it was too late to change it. After my first session, I quickly moved to the other room and setup my main laptop, a Dell Precision. We tested the video output (VGA) and didn’t notice anything special. The projectors are using a fairly high resolution (kudos to the Basel conference center for not having old school 1024x768 projectors anymore, that makes Blend really hard to demo ;) but since everything went great during the first talk, I was not worried. In fact I even had some time to chat with some early attendees about my Microsoft Surface and the Samsung Slate 7, which I had carried with me in addition to the Precision. I just thought it would be nice to show the hardware that Windows 8 can run on, without thinking any further. When the session started, I immediately noticed that the main screen was not showing anything. I thought I had just forgotten to switch to “duplicate” for the video output, and did that with a quick Win-P. However it didn’t “hold”. After 2 seconds, it reverted back to a black display for my attendees. Then I started to really worry. We tried everything, switching from VGA to HDMI, changing the resolution, setting the projector as primary display, but nothing did the trick. The projector was just refusing to show my screen. Now, to show you how despaired I started to be, I even considered using the “extend” setting (which worked just fine), and to use one of the feedback monitors on the floor but really it was super cumbersome. Eventually, my last resort arrived: I started my Samsung Slate 7, which by chance has Visual Studio 12 and Blend 5 installed, plugged the HDMI projector in the dock (yes, I had the dock with me, which I usually don’t!), connected it to internet (had to enter a long password for that), loaded the source code from my main machine using a USB stick and…. finally started to give my presentation. All in all I think we lost about 10 minutes. Amongst the most horrible minutes of my whole life, truly (yes I am blessed, I didn’t have that many horrible minutes in my life ;) I really want to apologize to my attendees. We joked a bit during the attempts to resolve the issue, the reactions I had after the session were all very nice and sympathetic. Only a handful of people left my session while I was having the issues, and I really don’t blame them (who knew how long the problem would last!!). But still, I probably talked at more than 60 sessions over the years, and this was by far my most painful moment. What did I learn? So what did I learn from this? Well from now on I will always have my slate ready with the latest source code, internet connection and every tool I might need during the presentation. This way, if I detect even a hint that the Precision might not work, I will just switch to the Slate. The experience of presenting on the slate is actually not bad at all, it is just a bit slow for my taste, but it does work. By the way, I will be posting the code and slides for my sessions very soon, I just need to “clean it and zip it”. Stay tuned, and thanks again for your patience in that horrible circumstance. Cheers Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • MVVM Light V4 preview 2 (BL0015) #mvvmlight

    - by Laurent Bugnion
    Over the past few weeks, I have worked hard on a few new features for MVVM Light V4. Here is a second early preview (consider this pre-alpha if you wish). The features are unit-tested, but I am now looking for feedback and there might be bugs! Bug correction: Messenger.CleanupList is now thread safe This was an annoying bug that is now corrected: In some circumstances, an exception could be thrown when the Messenger’s recipients list was cleaned up (i.e. the “dead” instances were removed). The method is called now and then and the exception was thrown apparently at random. In fact it was really a multi-threading issue, which is now corrected. Bug correction: AllowPartiallyTrustedCallers prevents EventToCommand to work This is a particularly annoying regression bug that was introduced in BL0014. In order to allow MVVM Light to work in XBAPs too, I added the AllowPartiallyTrustedCallers attribute to the assemblies. However, we just found out that this causes issues when using EventToCommand. In order to allow EventToCommand to continue working, I reverted to the previous state by removing the AllowPartiallyTrustedCallers attribute for now. I will work with my friends at Microsoft to try and find a solution. Stay tuned. Bug correction: XML documentation file is now generated in Release configuration The XML documentation file was not generated for the Release configuration. This was a simple flag in the project file that I had forgotten to set. This is corrected now. Applying EventToCommand to non-FrameworkElements This feature has been requested in order to be able to execute a command when a Storyboard is completed. I implemented this, but unfortunately found out that EventToCommand can only be added to Storyboards in Silverlight 3 and Silverlight 4, but not in WPF or in Windows Phone 7. This obviously limits the usefulness of this change, but I decided to publish it anyway, because it is pretty damn useful in Silverlight… Why not in WPF? In WPF, Storyboards added to a resource dictionary are frozen. This is a feature of WPF which allows to optimize certain objects for performance: By freezing them, it is a contract where we say “this object will not be modified anymore, so do your perf optimization on them without worrying too much”. Unfortunately, adding a Trigger (such as EventTrigger) to an object in resources does not work if this object is frozen… and unfortunately, there is no way to tell WPF not to freeze the Storyboard in the resources… so there is no way around that (at least none I can see. In Silverlight, objects are not frozen, so an EventTrigger can be added without problems. Why not in WP7? In Windows Phone 7, there is a totally different issue: Adding a Trigger can only be done to a FrameworkElement, which Storyboard is not. Here I think that we might see a change in a future version of the framework, so maybe this small trick will work in the future. Workaround? Since you cannot use the EventToCommand on a Storyboard in WPF and in WP7, the workaround is pretty obvious: Handle the Completed event in the code behind, and call the Command from there on the ViewModel. This object can be obtained by casting the DataContext to the ViewModel type. This means that the View needs to know about the ViewModel, but I never had issues with that anyway. New class: NotifyPropertyChanged Sometimes when you implement a model object (for example Customer), you would like to have it implement INotifyPropertyChanged, but without having all the frills of a ViewModelBase. A new class named NotifyPropertyChanged allows you to do that. This class is a simple implementation of INotifyPropertyChaned (with all the overloads of RaisePropertyChanged that were implemented in BL0014). In fact, ViewModelBase inherits NotifyPropertyChanged. ViewModelBase does not implement IDisposable anymore The IDisposable interface and the Dispose method had been marked obsolete in the ViewModelBase class already in V3. Now they have been removed. Note: By this, I do not mean that IDisposable is a bad interface, or that it shouldn’t be used on viewmodels. In the contrary, I know that this interface is very useful in certain circumstances. However, I think that having it by default on every instance of ViewModelBase was sending a wrong message. This interface has a strong meaning in .NET: After Dispose has been executed, the instance should not be used anymore, and should be ready for garbage collection. What I really wanted to have on ViewModelBase was rather a simple cleanup method, something that can be executed now and then during runtime. This is fulfilled by the ICleanup interface and its Cleanup method. If your ViewModels need IDisposable, you can still use it! You will just have to implement the interface on the class itself, because it is not available on ViewModelBase anymore. What’s next? I have a couple exciting new features implemented already but that need more testing before they go live… Just stay tuned and by MIX11 (12-14 April 2011), we should see at least a major addition to MVVM Light Toolkit, as well as another smaller feature which is pretty cool nonetheless More about this later! Happy Coding Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • An error when installing MVVM Light templates for VS10 Express

    - by Laurent Bugnion
    If you tried to install the Visual Studio 2010 Express project and item templates of MVVM Light V3 SP1 (with the Windows Phone tools hotfix), you may have encountered an error when unzipping the package, telling you that a file was corrupted. This error was reported to me a couple of times, and I was able to reproduce the issue. I just published a new version that takes care of this issue. If you encountered that error when installing, please download the new version and try again. Note that the error was only there for the Visual Studio 2010 Express version of the templates. No other changes were made.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Sample code and slides for my TechDays10 (Belgium) talks

    - by Laurent Bugnion
    The source code for my MVVM talk titled “Understanding the MVVM Pattern” given at TechDays 2010 in Antwerpen, Belgium, is available online. It is actually the same code than the MIX10 one, but I added the Windows Phone 7 MVVM Light application (available in the folder titled “Mix10.MvvmDemo2-End”. Note: before unpacking the zip file, you should right click on it, and select properties / Unblock. I also published the slides for my two talks: Understanding the MVVM Pattern A day in the life of a WPF/SL integrator As far as I know, the videos will be online soon, stay tuned and I will announce when it is the case. Get Started page for the MVVM Light Toolkit: http://www.galasoft.ch/mvvm/getstarted   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Navigation in a #WP7 application with MVVM Light

    - by Laurent Bugnion
    In MVVM applications, it can be a bit of a challenge to send instructions to the view (for example a page) from a viewmodel. Thankfully, we have good tools at our disposal to help with that. In his excellent series “MVVM Light Toolkit soup to nuts”, Jesse Liberty proposes one approach using the MVVM Light messaging infrastructure. While this works fine, I would like to show here another approach using what I call a “view service”, i.e. an abstracted service that is invoked from the viewmodel, and implemented on the view. Multiple kinds of view services In fact, I use view services quite often, and even started standardizing them for the Windows Phone 7 applications I work on. If there is interest, I will be happy to show other such view services, for example Animation services, responsible to start/stop animations on the view. Dialog service, in charge of displaying messages to the user and gathering feedback. Navigation service, in charge of navigating to a given page directly from the viewmodel. In this article, I will concentrate on the navigation service. The INavigationService interface In most WP7 apps, the navigation service is used in quite a straightforward way. We want to: Navigate to a given URI. Go back. Be notified when a navigation is taking place, and be able to cancel. The INavigationService interface is quite simple indeed: public interface INavigationService { event NavigatingCancelEventHandler Navigating; void NavigateTo(Uri pageUri); void GoBack(); } Obviously, this interface can be extended if necessary, but in most of the apps I worked on, I found that this covers my needs. The NavigationService class It is possible to nicely pack the navigation service into its own class. To do this, we need to remember that all the PhoneApplicationPage instances use the same instance of the navigation service, exposed through their NavigationService property. In fact, in a WP7 application, it is the main frame (RootFrame, of type PhoneApplicationFrame) that is responsible for this task. So, our implementation of the NavigationService class can leverage this. First the class will grab the PhoneApplicationFrame and store a reference to it. Also, it registers a handler for the Navigating event, and forwards the event to the listening viewmodels (if any). Then, the NavigateTo and the GoBack methods are implemented. They are quite simple, because they are in fact just a gateway to the PhoneApplicationFrame. The whole class is as follows: public class NavigationService : INavigationService { private PhoneApplicationFrame _mainFrame; public event NavigatingCancelEventHandler Navigating; public void NavigateTo(Uri pageUri) { if (EnsureMainFrame()) { _mainFrame.Navigate(pageUri); } } public void GoBack() { if (EnsureMainFrame() && _mainFrame.CanGoBack) { _mainFrame.GoBack(); } } private bool EnsureMainFrame() { if (_mainFrame != null) { return true; } _mainFrame = Application.Current.RootVisual as PhoneApplicationFrame; if (_mainFrame != null) { // Could be null if the app runs inside a design tool _mainFrame.Navigating += (s, e) => { if (Navigating != null) { Navigating(s, e); } }; return true; } return false; } } Exposing URIs I find that it is a good practice to expose each page’s URI as a constant. In MVVM Light applications, a good place to do that is the ViewModelLocator, which already acts like a central point of setup for the views and their viewmodels. Note that in some cases, it is necessary to expose the URL as a string, for instance when a query string needs to be passed to the view. So for example we could have: public static readonly Uri MainPageUri = new Uri("/MainPage.xaml", UriKind.Relative); public const string AnotherPageUrl = "/AnotherPage.xaml?param1={0}&param2={1}"; Creating and using the NavigationService Normally, we only need one instance of the NavigationService class. In cases where you use an IOC container, it is easy to simply register a singleton instance. For example, I am using a modified version of a super simple IOC container, and so I can register the navigation service as follows: SimpleIoc.Register<INavigationService, NavigationService>(); Then, it can be resolved where needed with: SimpleIoc.Resolve<INavigationService>(); Or (more frequently), I simply declare a parameter on the viewmodel constructor of type INavigationService and let the IOC container do its magic and inject the instance of the NavigationService when the viewmodel is created. On supported platforms (for example Silverlight 4), it is also possible to use MEF. Or, of course, we can simply instantiate the NavigationService in the ViewModelLocator, and pass this instance as a parameter of the viewmodels’ constructor, injected as a property, etc… Once the instance has been passed to the viewmodel, it can be used, for example with: NavigationService.NavigateTo(ViewModelLocator.ComparisonPageUri); Testing Thanks to the INavigationService interface, navigation can be mocked and tested when the viewmodel is put under unit test. Simply implement and inject a mock class, and assert that the methods are called as they should by the viewmodel. Conclusion As usual, there are multiple ways to code a solution answering your needs. I find that view services are a really neat way to delegate view-specific responsibilities such as animation, dialogs and of course navigation to other classes through an abstracted interface. In some cases, such as the NavigationService class exposed here, it is even possible to standardize the implementation and pack it in a class library for reuse. I hope that this sample is useful! Happy coding. Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Adventures in Windows 8: Solving activation errors

    - by Laurent Bugnion
    Note: I tagged this article with “MVVM” because I got a few support requests for MVVM Light regarding this exact issue. In fact it is a Windows 8 issue and has nothing to do with MVVM Light per se… Sometimes when you work on a Windows 8 app, you will get a very annoying issue when starting the app. In that case, the app doesn’t not even start past the Splash screen. Putting a breakpoint in App.xaml.cs doesn’t help because the app doesn’t even reach that point! So what exactly is happening? Well when a Windows 8 app starts, the system is performing a few check first. One of the checks, for instance, is to see if an app with the same package ID is already available. The package ID is a unique value set in the package manifest. In the Solution Explorer, double click on Package.appxmanifest. This opens the manifest in a special editor Click on the Packaging tab See the GUID under Package Name. This is the unique ID I am talking about. If there is a conflict (i.e. if an app is already installed with the exact same ID), Windows will warm the user that the app is already installed. However when you are in the process of developing an app, you install and uninstall the same app many many times (every time that you start in Visual Studio), and sometimes some issues arise, for instance failing to uninstall the app before starting the new instance of the same app. First step if you get such an error When the application fails to start past the splash screen, the first step is to identify what kind of error happened. In my experience the “already installed” is by far the most frequent (in fact I never had another such error), but it can be something else. An annoying thing is that the popup that shows the error is usually started below the Windows 8 app, and so you don’t even see it! This is especially true if you run this in the Simulator. In that case, do the following: Press on the Simulator’s home button, then press on the Desktop tile on the Start menu. The error popup should be shown on the desktop. If your applications runs on the Local machine, you also do the same and press the Windows button, and then from the Start menu press the Desktop tile. Deployment error in Studio Sometimes the same error causes Visual Studio to fail launching the application at all with a deployment error. This is a better case, because at least it is clear that there is an issue. In that case, write down the code that is shown in the Error window (for instance 0x80073D05 in the example below). Once you have the error code, go to the “Troubleshooting packaging, deployment, and query of Windows Store apps” page and look up the code in question. In my case, the error was “ERROR_DELETING_EXISTING_APPLICATIONDATA_STORE_FAILED”, “An error occurred while deleting the package's previously existing application data.” Solving the “ERROR_DELETING_EXISTING_APPLICATIONDATA_STORE_FAILED” issue Update: Before trying the below, you can also try the simple steps: Exit Visual Studio Go to the Start menu Locate your app’s tile. It should be visible in the Start menu directly, towards the far end on the right. Right click the tile and select Uninstall from the App Bar. Restart Visual Studio and try again. Sometimes it helps. If it doesn’t, then try the following: In order to solve the case where Windows, for any reason, fails to delete the existing application before starting the new instance, follow the steps: Open the Package.appxmanifest in Visual Studio Open the Packaging tab. Change the Package name. For tests you can just try to change the last character of the GUID, though I would recommend creating a brand new GUID. Press Start Type GUID Start the GUID Generator application Select Registry Format Press Copy. Paste the new GUID in place of the Package Name in Visual Studio Important: don’t forget to remove the curly brackets at the beginning and at the end of the newly pasted GUID. Then you just have to cross your fingers and start the application again… If it works, celebrate. if it doesn’t work… well at this point I am not sure so good luck with that ;) Happy coding, Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Get your picture on the screen at MIX11: Help me create a repository of sample data

    - by Laurent Bugnion
    Here is your chance to get your picture on the big screen during my MIX11 presentation in April this year. I need to create a small repository of sample data for my demos. So instead of tapping in my imagination and creating dummy users (or reusing past information I already used in other demos), I thought I would appeal to the amazing community: Send me an email with the following information. I will include the first 30 users into my sample data repository and use your info in my demo. First Name Last Name Date of birth Picture Link to Facebook profile (optional) Disclaimer: The data will only be running locally on my hard drive. The demos will however be filmed and the videos made public. By providing this information, you explicitly consent to this data being used in demos at MIX11 and possibly in following conferences. The data will only be used for demo purposes. Thanks for your help!!   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • &ldquo;Using the MVVM pattern in Windows 8&rdquo; in MSDN Magazine

    - by Laurent Bugnion
    These days I am swimming in Windows 8 code, and I must say it is a good feeling. This gives me the occasion to push MVVM Light and a few other components of mine to their limits, and to fix or improve a few things on the fly. All this goodness will be available in V4.1 which is scheduled shortly after Windows 8 launch. In spite of the busy schedule, I couldn’t resist writing an article for MSDN magazine about, you guessed it, the MVVM pattern and MVVM Light in Windows 8. It is an article that goes quite in depth in some of the concepts, and provides an app demonstrating how to use them. The article is available for free in the special Windows 8 edition of MSDN magazine that just came out today. Enjoy!       Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Adventures in Windows 8: Working around the navigation animation issues in LayoutAwarePage

    - by Laurent Bugnion
    LayoutAwarePage is a pretty cool add-on to Windows 8 apps, which facilitates greatly the implementation of orientation-aware (portrait, landscape) as well as state-aware (snapped, filled, fullscreen) apps. It has however a few issues that are obvious when you use transformed elements on your page. Adding a LayoutAwarePage to your application If you start with a blank app, the MainPage is a vanilla Page, with no such feature. In order to have a LayoutAwarePage into your app, you need to add this class (and a few helpers) with the following operation: Right click on the Solution and select Add, New Item from the context menu. From the dialog, select a Basic Page (not a Blank Page, which is another vanilla page). If you prefer, you can also use Split Page, Items Page, Item Detail Page, Grouped Items Page or Group Detail Page which are all LayoutAwarePages. Personally I like to start with a Basic Page, which gives me more creative freedom. Adding this new page will cause Visual Studio to show a prompt asking you for permission to add additional helper files to the Common folder. One of these helpers in the LayoutAwarePage class, which is where the magic happens. LayoutAwarePage offers some help for the detection of orientation and state (which makes it a pleasure to design for all these scenarios in Blend, by the way) as well as storage for the navigation state (more about that in a future article). Issue with LayoutAwarePage When you use UI elements such as a background picture, a watermark label, logos, etc, it is quite common to do a few things with those: Making them partially transparent (this is especially true for background pictures; for instance I really like a black Page background with a half transparent picture placed on top of it). Transforming them, for instance rotating them a bit, scaling them, etc. Here is an example with a picture of my two beautiful daughters in the Bird Park in Kuala Lumpur, as well as a transformed TextBlock. The image has an opacity of 40% and the TextBlock a simple RotateTransform. If I create an application with a MainPage that navigates to this LayoutAwarePage, however, I will have a very annoying effect: The background picture appears with an Opacity of 100%. The TextBlock is not rotated. This lasts only for less than a second (during the navigation animation) before the elements “snap into place” and get their desired effect. Here is the XAML that cause the annoying effect: <common:LayoutAwarePage x:Name="pageRoot" x:Class="App13.BasicPage1" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:common="using:App13.Common" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d"> <Grid Style="{StaticResource LayoutRootStyle}"> <Grid.RowDefinitions> <RowDefinition Height="140" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <Image Source="Assets/el20120812025.jpg" Stretch="UniformToFill" Opacity="0.4" Grid.RowSpan="2" /> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" /> <ColumnDefinition Width="*" /> </Grid.ColumnDefinitions> <Button x:Name="backButton" Click="GoBack" IsEnabled="{Binding Frame.CanGoBack, ElementName=pageRoot}" Style="{StaticResource BackButtonStyle}" /> <TextBlock x:Name="pageTitle" Grid.Column="1" Text="Welcome" Style="{StaticResource PageHeaderTextStyle}" /> </Grid> <TextBlock HorizontalAlignment="Center" TextWrapping="Wrap" Text="Welcome to my Windows 8 Application" Grid.Row="1" VerticalAlignment="Bottom" FontFamily="Segoe UI Light" FontSize="70" FontWeight="Light" TextAlignment="Center" Foreground="#FFFFA200" RenderTransformOrigin="0.5,0.5" UseLayoutRounding="False" d:LayoutRounding="Auto" Margin="0,0,0,153"> <TextBlock.RenderTransform> <CompositeTransform Rotation="-6.545" /> </TextBlock.RenderTransform> </TextBlock> <VisualStateManager.VisualStateGroups> [...] </VisualStateManager.VisualStateGroups> </Grid> </common:LayoutAwarePage> Solving the issue In order to solve this “snapping” issue, the solution is to wrap the elements that are transformed into an empty Grid. Honestly, to me it sounds like a bug in the LayoutAwarePage navigation animation, but thankfully the workaround is not that difficult: Simple change the main Grid as follows: <Grid Style="{StaticResource LayoutRootStyle}"> <Grid.RowDefinitions> <RowDefinition Height="140" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <Grid Grid.RowSpan="2"> <Image Source="Assets/el20120812025.jpg" Stretch="UniformToFill" Opacity="0.4" /> </Grid> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" /> <ColumnDefinition Width="*" /> </Grid.ColumnDefinitions> <Button x:Name="backButton" Click="GoBack" IsEnabled="{Binding Frame.CanGoBack, ElementName=pageRoot}" Style="{StaticResource BackButtonStyle}" /> <TextBlock x:Name="pageTitle" Grid.Column="1" Text="Welcome" Style="{StaticResource PageHeaderTextStyle}" /> </Grid> <Grid Grid.Row="1"> <TextBlock HorizontalAlignment="Center" TextWrapping="Wrap" Text="Welcome to my Windows 8 Application" VerticalAlignment="Bottom" FontFamily="Segoe UI Light" FontSize="70" FontWeight="Light" TextAlignment="Center" Foreground="#FFFFA200" RenderTransformOrigin="0.5,0.5" UseLayoutRounding="False" d:LayoutRounding="Auto" Margin="0,0,0,153"> <TextBlock.RenderTransform> <CompositeTransform Rotation="-6.545" /> </TextBlock.RenderTransform> </TextBlock> </Grid> <VisualStateManager.VisualStateGroups> [...] </Grid> Hopefully this will help a few people, I banged my head on the wall for a while before someone at Microsoft pointed me to the solution ;) Happy coding, Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Silverlight TV 13: MVVM Light Toolkit

    The latest episode of Silverlight TV is now available on Channel 9! In this episode, Silverlight MVP Laurent Bugnion of IdentityMine appears on the show to discuss using MVVM with Silverlight. Laurent and John discuss their experiences with MVVM and how Laurent's experiences inspired him to create his MVVM Light Toolkit. If you have been meaning to get into MVVM or you feel a bit overwhelmed by it all, definitely watch this episode and check out the MVVM Light Toolkit. Links for this episode:...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • MVVM Light V3 released at #MIX10

    - by Laurent Bugnion
    During my session “Understanding the MVVM pattern” at MIX10 in Vegas, I showed some components of the MVVM Light toolkit V3, which gave me the occasion to announce the release of version 3. This version has been in alpha stage for a while, and has been tested by many users. it is very stable, and ready for a release. So here we go! What’s new What’s new in MVVM Light Toolkit V3 is the topic of the next post. Cleaning up I would recommend cleaning up older versions before installing V3. I prepared a page explaining how to do that manually. Unfortunately I didn’t have time to create an automatic cleaner/installer, this is very high on my list but with the book and the conferences going on, it will take a little more time. Cleaning up is recommended because I changed the name of some DLLs to avoid some confusion (between the WPF3.5 and WPF4 version, as well as between the SL3 and SL4 versions). More details in the section titled “Compatibility”. Installation Installing MVVM Light toolkit is the manual process of unzipping a few files. The installation page has been updated to reflect the newest information. Compatibility MVVM Light toolkit V3 has components for the following environments and frameworks: Visual Studio 2008: Silverlight 3 Windows Presentation Foundation 3.5 SP1 Expression Blend 3 Silverlight 3 Windows Presentation Foundation 3.5 SP1 Visual Studio 2010 RC Silverlight 3 Silverlight 4 Windows Presentation Foundation 3.5 SP1 Windows Presentation Foundation 4 Silverlight for Windows Phone 7 series Expression Blend 4 beta Silverlight 3 Silverlight 4 Windows Presentation Foundation 3.5 SP1 Windows Presentation Foundation 4 Feedback As usual I welcome your constructive feedback. If you want the issue to be discussed in public, the best way is through the discussion page on the Codeplex site. if you wish to keep the conversation private, please check my Contact page for ways to talk to me. Video, tutorials There are a few new videos and tutorials available for the MVVM Light toolkit. The material is listed on the Get Started page, under “tutorials”.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Schedule for my session at MIX10

    - by Laurent Bugnion
    Microsoft has published the schedule for the MIX10 sessions. I have a sweet spot, and I dearly hope that it stays this way (Last year I had a great spot, but it was changed last minute and then I had a much better one, “competing” against Vertigo and their Playboy app… yeah try to explain to a bunch of geeks that MVVM is better than Playboy… good luck with that ;) Anyway, this year my sweet spot is on the very first day of the conference (there are workshops on Sunday, but this qualifies as pre-conference), Monday after the keynote which should get everyone pumped and excited. Schedule and location I would be really happy to meet y’all at Understanding the Model-View-ViewModel Pattern in Lagoon F on Monday at 2:00 PM http://live.visitmix.com/MIX10/Sessions/EX14 See you in Vegas (or in video…) Everything I saw so far hints that this should be a very, very exciting edition of MIX, maybe the most electrifying ever. The great news is that everything will be available even if you cannot make it: The keynotes are typically streamed live, and if you remember last year’s experience at PDC, it is a really good alternative. Built with Silverlight, the feed uses smooth streaming (adjusting the quality according to your bandwidth automatically), possibility to pause and rewind if you miss something, and a great picture quality. As for the sessions, the message at MIX is that the videos will be available online approximately 24 hours after the session is being held. This is a great feat! So, see you in Vegas (or in video)! Cheers, Laurent

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  • What&rsquo;s new in MVVM Light V3

    - by Laurent Bugnion
    V3 of the MVVM Light Toolkit was released during MIX10, after quite a long alpha stage. This post lists the new features in MVVM Light V3. Compatibility MVVM Light Toolkit V3 can be installed for the following tools and framework versions: Visual Studio 2008 SP1, Expression Blend 3 Windows Presentation Foundation 3.5 SP1 Silverlight 3 Visual Studio 2010 RC, Expression Blend 4 beta Windows Presentation Foundation 3.5 SP1 Windows Presentation Foundation 4 RC Silverlight 3 Silverlight 4 RC For more information about installing the MVVM Light Toolkit V3, please visit this page. For cleaning up existing installation, see this page. New in V3 RTM The following features have been added after V3 alpha3: Project template for the Windows Phone 7 series (Silverlight) This new template allows you to create a new MVVM Light application in Visual Studio 2010 RC and to run it in the Windows Phone 7 series emulator. This template uses the Silverlight 3 version of the MVVM Light Toolkit V3. At this time, only the essentials features of the GalaSoft.MvvmLight.dll assembly are supported on the phone. New in V3 alpha3 The following features have been added after V3 alpha2: New logo An awesome logo has been designed for MVVM Light by Philippe Schutz. DispatcherHelper class (in GalaSoft.MvvmLight.Extras.dll) This class is useful when you work on multi-threaded WPF or Silverlight applications. Initializing: The DispatcherHelper class must be initialized in the UI thread. For example, you can initialize the class in a Silverlight application’s Application_Startup event handler, or in the WPF application’s static App constructor (in App.xaml). // Initializing in Silverlight (in App.xaml) private void Application_Startup( object sender, StartupEventArgs e) { RootVisual = new MainPage(); DispatcherHelper.Initialize(); } // Initializing in WPF (in App.xaml) static App() { DispatcherHelper.Initialize(); } Verifying if a property exists The ViewModelBase.RaisePropertyChanged method now checks if a given property name exists on the ViewModel class, and throws an exception if that property cannot be found. This is useful to detect typos in a property name, for example during a refactoring. Note that the check is only done in DEBUG mode. Replacing IDisposable with ICleanup The IDisposable implementation in the ViewModelBase class has been marked obsolete. Instead, the ICleanup interface (and its Cleanup method) has been added. Implementing IDisposable in a ViewModel is still possible, but must be done explicitly. IDisposable in ViewModelBase was a bad practice, because it supposes that the ViewModel is garbage collected after Dispose is called. instead, the Cleanup method does not have such expectation. The ViewModelLocator class (created when an MVVM Light project template is used in Visual Studio or Expression Blend) exposes a static Cleanup method, which should in turn call each ViewModel’s Cleanup method. The ViewModel is free to override the Cleanup method if local cleanup must be performed. Passing EventArgs to command with EventToCommand The EventToCommand class is used to bind any event to an ICommand (typically on the ViewModel). In this case, it can be useful to pass the event’s EventArgs parameter to the command in the ViewModel. For example, for the MouseEnter event, you can pass the MouseEventArgs to a RelayCommand<MouseEventArgs> as shown in the next listings. Note: Bringing UI specific classes (such as EventArgs) into the ViewModel reduces the testability of the ViewModel, and thus should be used with care. Setting EventToCommand and PassEventArgsToCommand: <Grid x:Name="LayoutRoot"> <i:Interaction.Triggers> <i:EventTrigger EventName="MouseEnter"> <cmd:EventToCommand Command="{Binding MyCommand}" PassEventArgsToCommand="True" /> </i:EventTrigger> </i:Interaction.Triggers> </Grid> Getting the EventArgs in the command public RelayCommand<MouseEventArgs> MyCommand { get; private set; } public MainViewModel() { MyCommand = new RelayCommand<MouseEventArgs>(e => { // e is of type MouseEventArgs }); } Changes to templates Various changes have been made to project templates and item templates to make them more compatible with Silverlight 4 and to improve their visibility in Visual Studio and Expression Blend. Bug corrections When a message is sent through the Messenger class using the method Messenger.Default.Send<T>(T message, object token), and the token is a simple value (for example int), the message was not sent correctly. This bug is now corrected. New in V3 The following features have been added after V2. Sending messages with callback Certain classes have been added to the GalaSoft.MvvmLight.Messaging namespace, allowing sending a message and getting a callback from the recipient. These classes are: NotificationMessageWithCallback: Base class for messages with callback. NotificationMessageAction: A class with string notification, and a parameterless callback. NotificationMessageAction<T>: A class with string notification, and a callback with a parameter of type T. To send a message with callback, use the following code: var message = new NotificationMessageAction<bool>( "Hello world", callbackMessage => { // This is the callback code if (callbackMessage) { // ... } }); Messenger.Default.Send(message); To register and receive a message with callback, use the following code: Messenger.Default.Register<NotificationMessageAction<bool>>( this, message => { // Do something // Execute the callback message.Execute(true); }); Messenger.Default can be overriden The Messenger.Default property can also be replaced, for example for unit testing purposes, by using the Messenger.OverrideDefault method. All the public methods of the Messenger class have been made virtual, and can be overridden in the test messenger class. Sending messages to interfaces In V2, it was possible to deliver messages targeted to instances of a given class. in V3 it is still possible, but in addition you can deliver a message to instances that implement a certain interface. The message will not be delivered to other recipients. Use the overload Messenger.Default.Send<TMessage, TTarget>(TMessage message) where TTarget is, in fact, an interface (for example IDisposable). Of course the recipient must register to receive the type of message TMessage. Sending messages with a token Messages can now be sent through the Messenger with a token. To send a message with token, use the method overload Send<TMessage>(TMessage message, object token). To receive a message with token, use the methods Register<TMessage>(object recipient, object token, Action<TMessage> action) or Register<TMessage>(object recipient, object token, bool receiveDerivedMessagesToo, Action<TMessage> action) The token can be a simple value (int, string, etc…) or an instance of a class. The message is not delivered to recipients who registered with a different token, or with no token at all. Renaming CommandMessage to NotificationMessage To avoid confusion with ICommand and RelayCommand, the CommandMessage class has been renamed to NotificationMessage. This message class can be used to deliver a notification (of type string) to a recipient. ViewModelBase constructor with IMessenger The ViewModelBase class now accepts an IMessenger parameter. If this constructor is used instead of the default empty constructor, the IMessenger passed as parameter will be used to broadcast a PropertyChangedMessage when the method RaisePropertyChanged<T>(string propertyName, T oldValue, T newValue, bool broadcast) is used. In the default ViewModelBase constructor is used, the Messenger.Default instance will be used instead. EventToCommand behavior The EventToCommand behavior has been added in V3. It can be used to bind any event of any FrameworkElement to any ICommand (for example a RelayCommand located in the ViewModel). More information about the EventToCommand behavior can be found here and here. Updated the project templates to remove the sample application The project template has been updated to remove the sample application that was created every time that a new MVVM Light application was created in Visual Studio or Blend. This makes the creation of a new application easier, because you don’t need to remove code before you can start writing code. Bug corrections Some bugs that were in Version 2 have been corrected: In some occasions, an exception could be thrown when a recipient was registered for a message at the same time as a message was received. New names for DLLs If you upgrade an existing installation, you will need to change the reference to the DLLs in C:\Program Files\Laurent Bugnion (GalaSoft)\Mvvm Light Toolkit\Binaries. The assemblies have been moved, and the versions for Silverlight 4 and for WPF4 have been renamed, to avoid some confusion. It is now easier to make sure that you are using the correct DLL. WPF3.5SP1, Silverlight 3 When using the DLLs, make sure that you use the correct versions. WPF4, Silverlight 4 When using the DLLs, make sure that you use the correct versions.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Be careful when installing the Blend Windows Phone 7 Add-In

    - by Laurent Bugnion
    There was a small issue today with the release of the Windows Phone Developer Tools CTP (April 2010 Refresh) refresh. The issue is that the Expression Blend Add-in Preview for Windows Phone (April Refresh) is not compatible with Blend 4.0.20408.0, which was the public RC (release candidate). A few days ago, the Blend team released a fix for an issue that was sometimes causing a crash when Blend was starting up. This new release (V4.0.20421.0) was not very well announced however, and many people (including me) did not install it. After all, Blend did not crash at startup of either of my machines, so I didn’t deem necessary to install yet a new RC. However, it is now clear that the Windows Phone 7 Add-In needs this latest-and-greatest version to work. If you have Blend 4.0.20408.0, you won’t be able to work with Windows Phone 7 in Blend. To add to the confusion, the page where you can download V4.0.20421.0 from has an error, and the wrong version number is wrong (at least at the time of writing). Do not let this confuse you. You must download this version and install it. Hopefully this helps clarify some of the confusion… Happy WinPhone7 coding :) Laurent

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  • MVVM Light V4b1 for Windows 8 Consumer Preview (with installer)

    - by Laurent Bugnion
    I just pushed the following to Codeplex: A new MVVM Light project template for Windows 8 Consumer Preview. This template appears in the File, New Project dialog and allows you to create a Metro style app already wired with MVVM Light. An updated Windows 8 installer for MVVM Light. Preconditions: This installs MVVM Light for Windows 8 only. You can install it side-by-side with the standard MVVM Light for Silverlight, WPF and Windows Phone. Where do I get it? You can download the MSI from: http://mvvmlight.codeplex.com/releases/view/85317 What does it do? The installer installs the Windows 8 version of the MVVM Light DLLs, as well as a new project template for an MVVM Light Metro style app, and code snippets. What is missing? Since Windows 8 Developer Preview, I worked on porting the DispatcherHelper class, and it works now. However the EventToCommand behavior is still not available on Windows 8 (because behaviors are not supported on Windows 8 for the moment). Known issues Some testers reported issues with the code snippets installation. Code snippets should appear when you type “mvvm” in your C# code, there is a list of mvvm-prefixed snippets (such as mvvminpc, etc). If you do not see these snippets, please stay tuned, I am working on fixing this issue.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Small change in MVVM Light Toolkit templates for Blend 4 RC

    - by Laurent Bugnion
    Ah, the joy of new releases… You will find that the MVVM Light Toolkit works fine with Visual Studio 2010 RTM and Blend 4 RC except for a few adjustments: Blend templates The path to the Expression Blend 4 project templates changed. If you start Expression Blend 4 RC now, you will likely not see the MVVM Light templates in the New Project dialog.   New Project dialog with MVVM Light To restore the templates, follow the steps: Open Windows Explorer Navigate to C:\Users\[username]\Documents\Expression (or simply type My Documents in Windows Explorer and then open the Expression folder). Change the name of the “Blend 4 beta” folder into “Blend 4”. That’s it, you should now see the templates in the New Project dialog in Blend 4. Note that since the new name is “Blend 4”, I hope that I won’t need to do the same exercise when Blend 4 RTM is released! Windows Phone 7 templates Since the Windows Phone 7 tools are not ready yet for Visual Studio 2010 RTM and Blend 4 RC, the templates in the Silverlight for Windows Phone folders will not work. You will get an error if you try to create a new such project in the newly released environment. I hesitated to remove these templates from the current packages, but honestly that is a lot of trouble for a very short time before the tools for Windows Phone 7 are released (note: I don’t have any information as to when these tools will be released). In the mean time, just don’t create a WinPhone7 application. Reminder: If you want to write code for Windows Phone 7, you need to keep the Visual Studio 2010 RC as well as Expression Blend 4 beta. Updated package I uploaded an update to the Blend 4 templates. It is available like before on the “Install manually” page and on the Codeplex page.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • A fix for the design time error in MVVM Light V4.1

    - by Laurent Bugnion
    For those of you who installed V4.1 of MVVM Light and created a project for Windows Phone 8, you will have noticed an error showing up in the design surface (either in Visual Studio designer, or in Expression Blend). The error says: “Could not load type ‘System.ComponentModel.INotifyPropertyChanging’ from assembly ‘mscorlib.extensions’” with additional information about version numbers. The error is caused by an incompatibility between versions of System.Windows.Interactivity. Because this assembly is strongly named, any version incompatibility is causing the kind of error shown here (for an interesting discussion on the strong naming issue, see this thread on Codeplex). I managed to resolve the issue for Windows Phone 8 and will publish a cleaned up installer next week. In the mean time, in order to allow you to continue development, please follow the steps: Download the new DLLs zip package (MVVMLight_V4_1_25_WP8). Right click on the Zip file and select Properties from the context menu. Press the “Unblock” button (if available) and then OK. Right click again on the zip package and select “Extract all…”. Select a known location for the new DLLs. Open the MVVM Light project with the design time error in Visual Studio 2012. Open the References folder in the Solution Explorer. Select the following DLLs: GalaSoft.MvvmLight.dll, GalaSoft.MvvmLight.Extras.dll, Microsoft.Practices.ServiceLocation.dll and System.Windows.Interactivity.dll. Press “delete” and confirm to remove the DLLs from your project. Right click on References and select Add Reference from the context menu. Browse to the folder with the new DLLs. Select the four new DLLs and press OK. Rebuild your application, and open it again in Blend or in the Visual Studio designer. The error should be gone now. In the next few days, as time allows, I will publish a new MSI containing a fixed version of the DLLs as well as a few other improvements. This quick fix should however allow you to continue working on your Windows Phone 8 projects in design mode too.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • MVVM Light V4 preview (BL0014) release notes

    - by Laurent Bugnion
    I just pushed to Codeplex an update to the MVVM Light source code. This is an early preview containing some of the features that I want to release later under the version 4. If you find these features useful for your project, please download the source code and build the assemblies. I will appreciate greatly any issue report. This version is labeled “V4.0.0.0/BL0014”. The “BL” string is an old habit that we used in my days at Siemens Building Technologies, called a “base level”. Somehow I like this way of incrementing the “base level” independently of any other consideration (such as alpha, beta, CTP, RTM etc) and continue to use it to tag my software versions. In Microsoft parlance, you could say that this is an early CTP of MVVM Light V4. Caveat The code is unit tested, but as we all know this does not mean that there are no bugs This code has not yet been used in production. Again, your help in testing this is greatly appreciated, so please report all bugs to me! What’s new? The following features have been implemented: Misc Various “maintenance work”. All WPF assemblies (that is .NET35 and .NET4) now allow partially trusted callers. It means that you can use them in am XBAP in partial trust mode. Testing Various test updates Added Windows Phone 7 unit tests Note: For Windows Phone 7, due to an issue in the unit test framework, not all tests can be executed. I had to isolate those tests for the moment. The error was reported to Microsoft. ViewModelBase The constructor is now public to allow serialization (especially useful on the phone to tombstone the state). ViewModelBase.MessengerInstance now returns Messenger.Default unless it is set explicitly. Previously, MessengerInstance was returning null, which was complicating the code. Two new ways to raise the PropertyChanged event have been added. See below for details. Messenger Updated the IMessenger interface with all public members from the Messenger class. Previously some members were missing. A new Unregister method is now available, allowing to unregister a recipient for a given token. RelayCommand RaiseCanExecuteChanged now acts the same in Windows Presentation Foundation than in Silverlight. In previous versions, I was relying on the CommandManager to raise the CanExecuteChanged event in WPF. However, it was found to be too unreliable, and a more direct way of raising the event was found preferable. See below for details. Raising the PropertyChanged event A very much requested update is now included: the ability to raise the PropertyChanged event in a viewmodel without using “magic strings”. Personally, I don’t see strings as a major issue, thanks to two features of the MVVM Light Toolkit: In the DEBUG configuration, every time that the RaisePropertyChanged method is called, the name of the property is checked against all existing properties of the viewmodel. Should the property name be misspelled (because of a typo or refactoring), an exception is thrown, notifying the developer that something is wrong. To avoid impacting the performance, this check is only made in DEBUG configuration, but that should be enough to warn the developers in case they miss a rename. The property name is defined as a public constant in the “mvvminpc” code snippet. This allows checking the property name from another class (for example if the PropertyChanged event is handled in the view). It also allows changing the property name in one place only. However, these two safeguards didn’t satisfy some of the users, who requested another way to raise the PropertyChanged event. In V4, you can now do the following: Using lambdas private int _myProperty; public int MyProperty { get { return _myProperty; } set { if (_myProperty == value) { return; } _myProperty = value; RaisePropertyChanged(() => MyProperty); } } This raises the property changed event using a lambda expression instead of the property name. Light reflection is used to get the name. This supports Intellisense and can easily be refactored. You can also broadcast a PropertyChangedMessage using the Messenger.Default instance with: private int _myProperty; public int MyProperty { get { return _myProperty; } set { if (_myProperty == value) { return; } var oldValue = _myProperty; _myProperty = value; RaisePropertyChanged(() => MyProperty, oldValue, value, true); } } Using no arguments When the RaisePropertyChanged method is called within a setter, you can also omit the property name altogether. This will fail if executed outside of the setter however. Also, to avoid confusion, there is no way to broadcast the PropertyChangedMessage using this syntax. private int _myProperty; public int MyProperty { get { return _myProperty; } set { if (_myProperty == value) { return; } _myProperty = value; RaisePropertyChanged(); } } The old way Of course the “old” way is still supported, without broadcast: public const string MyPropertyName = "MyProperty"; private int _myProperty; public int MyProperty { get { return _myProperty; } set { if (_myProperty == value) { return; } _myProperty = value; RaisePropertyChanged(MyPropertyName); } } And with broadcast: public const string MyPropertyName = "MyProperty"; private int _myProperty; public int MyProperty { get { return _myProperty; } set { if (_myProperty == value) { return; } var oldValue = _myProperty; _myProperty = value; RaisePropertyChanged(MyPropertyName, oldValue, value, true); } } Performance considerations It is notorious that using reflection takes more time than using a string constant to get the property name. However, after measuring for all platforms, I found the differences to be very small. I will measure more and submit the results to the community for evaluation, because some of the results are actually surprising (for example, using the Messenger to broadcast a PropertyChangedMessage does not significantly increase the time taken to raise the PropertyChanged event and update the bindings). For now, I submit this code to you, and would be delighted to hear about your own results. Raising the CanExecuteChanged event manually In WPF, until now, the CanExecuteChanged event for a RelayCommand was raised automatically. Or rather, it was attempted to be raised, using a feature that is only available in WPF called the CommandManager. This class monitors the UI and when something occurs, it queries the state of the CanExecute delegate for all the commands. However, this proved unreliable for the purpose of MVVM: Since very often the value of the CanExecute delegate changes according to non-UI events (for example something changing in the viewmodel or in the model), raising the CanExecuteChanged event manually is necessary. In Silverlight, the CommandManager does not exist, so we had to raise the event manually from the start. This proved more reliable, and I now changed the WPF implementation of the RaiseCanExecuteChanged method to be the exact same in WPF than in Silverlight. For instance, if a command must be enabled when a string property is set to a value other than null or empty string, you can do: public MainViewModel() { MyTestCommand = new RelayCommand( () => DoSomething(), () => !string.IsNullOrEmpty(MyProperty)); } public const string MyPropertyName = "MyProperty"; private string _myProperty = string.Empty; public string MyProperty { get { return _myProperty; } set { if (_myProperty == value) { return; } _myProperty = value; RaisePropertyChanged(MyPropertyName); MyTestCommand.RaiseCanExecuteChanged(); } } Logo update I made a minor change to the logo: Some people found the lack of the word “light” (as in MVVM Light Toolkit) confusing. I thought it was cool, because the feather suggests the idea of lightness, however I can see the point. So I added the word “light” to the logo. Things should be quite clear now. What’s next? This is only the first of a series of releases that will bring MVVM Light to V4. In the next weeks, I will continue to add some very requested features and correct some issues in the code. I will probably continue this fashion of releasing the changes to the public as source code through Codeplex. I would be very interested to hear what you think of that, and to get feedback about the changes. Cheers, Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Prepping a conference

    - by Laurent Bugnion
    I have had the chance to talk at many conferences these past few years, and came up with a way to prepare them which works really well for me. Most importantly, it would make it quite easy to overcome an emergency (for example if my laptop would suddenly lose data). The whole code as well as the slides and other documents are in the cloud. I also use source control for my demos, so that I always have the latest and the greatest, but also a history of changes I made to my demos. Finally I have a system of code snippets which works great, and I often had very positive remarks from the audience regarding that. Putting everything in the cloud The one thing I used to be the most scared of was a sudden crash of my laptop, and being unable to restore in time for a conference. Most conferences ask speakers to send slides a few days (or weeks…) in advance, but let's face it, we all have last minute changes to our talks and I always come in the conference with updated slides that I pass to the management team. The answer to that dilemma used to be working off memory sticks, and that worked not bad. However last year I started putting all the documents relating to a conference in a DropBox folder, and that works great too. Obviously DropBox works only if you have connectivity, so if I for instance update slides while on an international flight, I cannot save to the cloud. The obvious answer to that is to backup everything on a memory stick… but I have to admit, I have been trusting my luck and working off my laptop HD and then synching everything to the cloud after landing. Of course on some US national flights you get WiFi on board, so in that case it is even simpler :) Usually after the conference is done, I remove the files from DropBox and copy them to their "final destination". They are backed up from there to BackBlaze, the great online backup service I am using routinely (I currently have about 90GB of data in BackBlaze). Outlining the presentations I like to have a written outline of my presentations written somewhere. I keep it simple, just write the various sections of the presentation with timing. I guess it is a remnant of the time when I was a private pilot, and using checklists for flight preparation. For example: Demo about designability 15' (0:37) Switch to Blend Open MainPage.xaml Create a DataTemplate ... Here I can immediately see during the presentation if I am taking too much time for my demo (0:37 is where I need to be when I am done with this section of the presentation, and 15' is the time that this particular section takes). I keep these sections reasonable, I don't detail every step of the preparation. Typically I have one such section for every 10-15 minutes of my talks. Yes, I am timing my presentations. I keep adjusting these numbers when I rehearse, and this really helps to feel more confident during the presentations. This is especially important for presentations that are long, like my MIX11 demo which clocked at 57 minutes (I had a lot of stuff to show…). Such presentations are risky, because if anything goes wrong, you will have to cut stuff, so the answer to that is: Rehearse, rehearse and when you're done rehearsing, rehearse a little more. I also have a "Preparation" section where I outline what I need to do before a presentation. For instance: Preparation Reboot in VHD Make sure MSN and Twitter are not running. Open VS10 and load demo Open Blend and load demo Run the WP7 emulator ... I typically start preparing my laptop an hour before the talk, starting everything I need to start and then putting my laptop to sleep. Saving and printing the outline, Timing Printing is a real problem because it is really hard to find a printer at most conference venues, and also quite hard in hotels. To solve that, I simply write everything in OneNote (synched to the cloud, now you start to know what I like ;) and then I print it to a PDF (I use CutePDFWriter) that I save to my Kindle. During the presentation, I read the outline off the Kindle (I mostly just need a quick check to see how I am timing). For timing during the presentation, I use the free tool ChronoGPS on my Windows Phone 7, but of course any phone these days has a clock/chrono application. In some conferences, they even have timers that the presenters can see, but they tend to count down and I prefer to count up… so I just use my own :) Source control for demos For demos, I create a separate folder and use Mercurial as source control. Mercurial has the huge advantage (over SVN or TFS) to work offline too, so I can commit while on a plane, and all the history is saved. Then when I have connectivity I push everything to the cloud (I am using the fantastic Trunksapp.com for my private repositories). Here too the obvious downside is the risk of losing my last changes if my laptop crashes before I can push to the cloud, and here too the obvious answer would be to work from a memory stick… though I have to admit I didn't do that lately (except when I was writing Silverlight 4 Unleashed, where I was really paranoid…) And code snippets? I am one of these presenters who hates to type in front of an audience. I can type really fast (writing two books has this advantage, it really teaches you to touch type and be fast at it) but in the context of an audience, on a stage where it is often damn cold (an issue I had a lot in past conferences, air conditioning can freeze your fingers and make it really hard to type), it doesn't work as well. I don't know for you, but I really dislike seeing a presentation where the speaker uses the backspace key more often than others ;) To solve that, I like to have my code ready in snippets, and drag them to the screen. Then I can spend time explaining each code snippet, while highlighting portions of the code (always highlight what you talk about, the audience often doesn't even see the cursor and doesn't know where you are on the screen!) Over the years I have used various solutions for code snippets, and now I have one which works really well… if you take a few precautions! I use the Visual Studio Toolbox. Preparing the code snippets You can store code snippets in the Toolbox for anything, XAML, C# etc. I arrange the snippets in the order in which I need them, which is a great way to remember what comes next in the presentation. I also separate them by topic, to make it easier to find them, for example when I switch to the slides and then back to the code. Remember that no matter how experienced you are, you will feel more nervous on stage than while you are preparing, so any way to make it easier for you is going to be beneficial to the audience. To store a code snippet, I do the following: Open the final demo that you want to show to the audience in Visual Studio. In your code, select a snippet of code that you want to explain in particular. Make sure that the Visual Studio Toolbox is open (menu View, Toolbox or Ctrl-Alt-X). Drag the selected snippet from the code window to the toolbox. (if needed) drag the snippet to the correct location (for example between two other code snippets so that you can access it as you speak through the demo). Right click on the snippet and select Rename Item from the context menu. Select a meaningful name. For me I use the following conventions: If it is a method, I use the method's name. If it is not a whole method, I use a descriptive name. If it is the content of a method (i.e. the body only, without the method's signature), I use "-> MethodName". This reminds me during the presentation that this is only the body, and that I need to insert that into an existing signature. This is the case, for instance, when I use Visual Studio to automatically generate the members of an interface’s implementation; then I only need to insert my snippet inside the generated method body. Saving the snippets This is the most important!! It happened to me a few times that VS10 lost its settings. When that happens, the snippets are lost too! Yeah that really sucks, especially (as it happened once) when this is the case about an hour before a talk… Stress and sweat follows, not good conditions to start a talk in front of an audience believe me. Thankfully, saving snippets is really easy with the following steps: Select the menu Tools, Import and Export Settings. Select Export selected environment settings and press Next. Uncheck All Settings. Then expand General Settings and select Toolbox (only!). Press Next. Select your source control folder and save under a meaningful name (for instance Snippets.vssettings). Commit to source control and push to the cloud. By the way, this also has the advantage of applying source control to the snippets file (which is an XML file), so you get history for free on that file! Reimporting the snippets If VS loses its settings and you need to reimport the snippets, this can be done super easily and very fast. Make sure that the Toolbox is empty. When you import snippets, they are merged with existing ones, they do not replace the content of the Toolbox. Unless merging is really what you want, make sure that your Toolbox is clean before you import, it is really easier. Select the menu Tools, Import and Export Settings. Select Import selected environment settings and press Next. Select No, just import new settings and press Next. Press Browse and select the Snippets.vssettings file. Press Finish. Et voila, all your snippets appear again in the Toolbox. Whew, the worst was averted and you can start your demo without sweating! (I had to do that once literally 5 minutes before the start of a demo, while my laptop was already hooked to the projector, and it went just fine). What about special tools? When using special tools (for example beta versions of tools you have an early access to), or a special configuration of your laptop, things can get tricky because you cannot really be sure that you will get a laptop with the same tools and the same configuration at the conference. To solve that, I use the following precautions: I make my demos from a Virtual Hard Disk. The great John Papa made a very easy-to-follow web page where he explains how to create a VHD and install Win7 to it. This gives you the full power of your laptop (as fast as booting from the metal). For me, I have a basic configuration that I saved on a USB harddrive (Win7 plus drivers, basic settings for desktop, folder options, taskbar etc) and Visual Studio 2010 SP1 on it. When preparing, I start by copying this "basis VHD" to my laptop. I install additional tools and configurations. I save the VHD back to the USB harddrive in a different folder. This would allow me to reinstall my demo environment quite fast, for example in case of harddrive failure. Replace the harddrive, copy the VHD to it, configure the BCD and you can start. Unfortunately this only works if the laptop itself still works. In the worst case of total failure, my security is to back all the installers up: The installers I use are synched on all my laptops and backed up to BackBlaze. If the worst happens and my laptop is absolutely broken, I can download the installer from BackBlaze and install on another laptop. This of course takes some time, and if that happens 5 minutes before a presentation, well… I don't have an answer to that, except of course crossing my fingers. Still, all that gives me additional security. Conclusion Remember folks, talking to an audience, large or small, will make you nervous. Just ask Scott Hanselman :) The goal here is to create the best possible conditions for you, and to create an environment where everything is saved and easy to restore, where everything is well known and provides you with additional confidence. The cooler you feel before the presentation (and during ;)), the better your presentation will be. Here too, the goal is to provide the best user experience you can have, which in turn will make it more enjoyable for your audience! Happy presenting :) Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Using commands with ApplicationBarMenuItem and ApplicationBarButton in Windows Phone 7

    - by Laurent Bugnion
    Unfortunately, in the current version of the Windows Phone 7 Silverlight framework, it is not possible to attach any command on the ApplicationBarMenuItem and ApplicationBarButton controls. These two controls appear in the Application Bar, for example with the following markup: <phoneNavigation:PhoneApplicationPage.ApplicationBar> <shell:ApplicationBar x:Name="MainPageApplicationBar"> <shell:ApplicationBar.MenuItems> <shell:ApplicationBarMenuItem Text="Add City" /> <shell:ApplicationBarMenuItem Text="Add Country" /> </shell:ApplicationBar.MenuItems> <shell:ApplicationBar.Buttons> <shell:ApplicationBarIconButton IconUri="/Resources/appbar.feature.video.rest.png" /> <shell:ApplicationBarIconButton IconUri="/Resources/appbar.feature.settings.rest.png" /> <shell:ApplicationBarIconButton IconUri="/Resources/appbar.refresh.rest.png" /> </shell:ApplicationBar.Buttons> </shell:ApplicationBar> </phoneNavigation:PhoneApplicationPage.ApplicationBar> This code will create the following UI: Application bar, collapsed Application bar, expanded ApplicationBarItems are not, however, controls. A quick look in MSDN shows the following hierarchy for ApplicationBarMenuItem, for example: Unfortunately, this prevents all the mechanisms that are normally used to attach a Command (for example a RelayCommand) to a control. For example, the attached behavior present in the class ButtonBaseExtension (from the Silverlight 3 version of the MVVM Light toolkit) can only be attached to a DependencyObject. Similarly, Blend behaviors (such as EventToCommand from the toolkit’s Extras library) needs a FrameworkElement to work. Using code behind The alternative is to use code behind. As I said in my MIX10 talk, the MVVM police will not take your family away if you use code behind (this quote was actually suggested to me by Glenn Block); the code behind is there for a reason. In our case, invoking a command in the ViewModel requires the following code: In MainPage.xaml: <shell:ApplicationBarMenuItem Text="My Menu 1" Click="ApplicationBarMenuItemClick"/> In MainPage.xaml.cs private void ApplicationBarMenuItemClick( object sender, System.EventArgs e) { var vm = DataContext as MainViewModel; if (vm != null) { vm.MyCommand.Execute(null); } } Conclusion Resorting to code behind to bridge the gap between the View and the ViewModel is less elegant than using attached behaviors, either through an attached property or through a Blend behavior. It does, however, work fine. I don’t have any information if future changes in the Windows Phone 7 Application Bar API will make this easier. In the mean time, I would recommend using code behind instead.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • My program at #MIX10

    - by Laurent Bugnion
    Getting ready to fly to Vegas and MIX10 is really an exciting time! It is also a very busy time, because we are working on a few projects that will be shown on stage, I have my presentation to prepare, and of course as always the book… though these days it has been a bit on the back burner to be honest ;) I arrive in Vegas on Sunday evening around 10PM, so I won’t be able to make it to the traditional IdentityMine dinner this year. I am sure it will be fun nonetheless! My session: Understanding the MVVM pattern http://live.visitmix.com/MIX10/Sessions/EX14 My session is scheduled on the first day, which is awesome, so I am crossing my fingers and hoping that the MIX team doesn’t change it at the last minute… The session will take place on Monday, the 15th of March, 2PM, Room Lagoon F Important: remember that the USA are moving to Summer time on Sunday, so don’t forget to adjust your watches!! Ask the Experts On Monday evening, I will attend the Ask the Experts event, which is taking place between 5Pm and 6:30PM in the main meal hall. This will be a great occasion to grab a beer and talk about code. The Commons MIX has a great place called the Commons, a great location to chill between sessions, and meet tons of interesting people. I love the Commons and plan to spend a lot of time there to meet as many people as I can. Parties I was invited to a few parties, and will do my best to avoid conflicts :) I plan to be at the following events: Silverlight Mixers on Monday evening Insiders MIX party on Tuesday Silverlight partner happy hour on Tuesday too This is a lot of fun, but at the same time we all know that the best value of a conference is to meet people face to face. This is just the right occasion.  And on Thursday… On Thursday I will be attending a Silverlight event at the Luxor. It will be a very busy day, perfect way to end the conference. I fly back home on Friday morning, but due to a long stop in Washington DC (where I intend to go downtown and take pictures… except if the weather is bad, in which case I will probably go to the museum of flight), I will reach home only on Sunday. Getting hold of me The best way to reach me during MIX is to send me a message on Twitter. I will regularly tweet my location at the conference, so make sure to come and meet me. I am eager to make new friends, to talk about the fantastic jobs we did in WPF and Silverlight over the past year and hear your war stories! http://www.twitter.com/lbugnion   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Oredev 2012: Summary and source code

    - by Laurent Bugnion
    This week, I had the pleasure to be invited to talk at Oredev, a really cool conference taking place in Malmo, Sweden. The whole event is awesome, including a very special dinner on Monday including sauna and swimming in a 6 degrees cold Baltic sea, and a reception with dinner at the town hall, including the mayor himself. Considering Malmo is a town of 300'000 inhabitants, it is a pretty nice occasion and the historical building itself is really worth seeing. For those interested, I placed my pictures on my Flickr account. I had a workshop on Tuesday morning about Windows 8 development with XAML/C#, and then a session on Wednesday about MVVM in Windows Phone 8 and Windows 8, of course using MVVM Light. I was very nervous because I reworked some of my demos as recently as this morning, in the wake of the Build conference last week and the release of both the Windows Phone SDK and MVVM Light V4.1. Everything went well however, and if I judge by the people I talked t after the talk, and Twitter, everything went pretty well. Before my talk on Tuesday, I had the pleasure to see a talk by Iris Classon (@irisclasson) on the challenges of being a "n00b" and a woman in software development. I especially appreciated her research and conclusions on the lack of women I our industry, a topic that is dear to my heart (because I want the best possible future for my two daughters, and also because I really enjoy working with women on projects, and getting a different insight on the art of software development. I really want to thank the excellent organization committee for their hard work and their fantastic welcome to Malmo. In particular Emily Holweck did a wonderful job and was super helpful throughout the preparation and the conference itself. I made a few pictures during my stay, all with the new Nokia Lumia 920, and hope you will enjoy them too. The source code and the slides… The source code is available for download from Skydrive. You will find the following: Windows 8 workshop slides. MVVM Applied slides Source code package with Win8Demo: The demo I built during the 4 hours workshop, with some light MVVM, web services (JSON), GridView, Design time data (Blend / Visual Studio designer), Bing maps integration, location sensor, Search pane integration. SemanticZoomSample: a sample I put together to demonstrate the SemanticZoom control, with two GridViews and of course full design time data for Blend work. Due to time constraints, I was not able to show this demo during the workshop, but I publish it anyway, hoping it will be useful to someone. PictureUploader: The demo I built during my 50 minutes session about MVVM Applied in Windows Phone 8 and Windows 8. Code sharing, design time data, MVVM Light are used in Windows Phone 8 and Windows 8 apps. And in video… You can also see the video of my MVVM talk thanks to the good services of the Oredev team! MVVM Applied in Windows Phone and Windows 8 from Øredev Conference on Vimeo.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • The gestures of Windows 8 (Consumer preview): part 2, More about Search

    - by Laurent Bugnion
    This is part 2 of a multipart blog post about the gestures and shortcuts in Windows 8 consumer preview. Part 1 can be found here! More about the Search charm In the first installment of this series, we talked about the charms and mentioned a few gestures to display the Search charm. Search is a very central and powerful feature in Windows 8, and allows you to search in Apps, Settings, Files and within Metro applications that support the Search contract. There are a few cool features around the Search, and especially the applications associated to it. I already mentioned the keyboard shortcuts you can use: Win-C shows the Charms bar (same as swiping from the right bevel towards the center of the screen). Win-Q open the Search fly out with Apps preselected. Win-W open the Search fly out with Settings preselected. Win-F open the Search fly out with Files preselected. Searching in Metro apps In addition to these three search domains, you can also search a Metro app, as long as it supports the Search contract (check this Build video to learn more about the Search contract). These apps show up in the Search flyout as shown here: Notice the list of apps below the Files button? That’s what we are talking about. First of all, the list order changes when you search in some applications. For instance, in the image above, I had used the Store with the Search charm. This is why the store shows up as the first app. I am not 100% what algorithm is used here (sorting according to number of searches is my guess), but try it out and try to figure it out Applications that have never been searched are sorted alphabetically. Does it mean we will see cool app names like ___AAA_MyCoolApp? I certainly hope not!! Pinning You can also pin often used apps to the Search flyout. To pin an app with the mouse, right click on it in the Search flyout and select Pin from the context menu. With the keyboard, use the arrow keys to go down to the selected app, and then open the context menu. With the finger, simply tap and hold until you see a semi transparent rectangle indicating that the context menu will be shown, then release. The context menu opens up and you can select Pin. Pin context menu Pinned apps Unpinning, Hiding Using the same technique as for pinning here above, you can also unpin a pinned application. Finally, you can also choose to hide an app from the Search flyout altogether. This is a convenient way to clean up and make it easy to find stuff. Note: At this point, I am not sure how to re-add a hidden app to the Search flyout. If anyone knows, please mention it in the comments, thanks! Reordering You can also reorder pinned apps. To do this, with the finger, tap, hold and pull the app to the side, then pull it vertically to reorder it. You can also reorder with the mouse, simply by clicking on an app and pulling it vertically to the place you want to put it. I don’t think there is a way to do that with the keyboard though. That’s it for now More gestures will follow in a next installment! Have fun with Windows 8   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Adventures in Windows 8: Understanding and debugging design time data in Expression Blend

    - by Laurent Bugnion
    One of my favorite features in Expression Blend is the ability to attach a Visual Studio debugger to Blend. First let’s start by answering the question: why exactly do you want to do that? Note: If you are familiar with the creation and usage of design time data, feel free to scroll down to the paragraph titled “When design time data fails”. Creating design time data for your app When a designer works on an app, he needs to see something to design. For “static” UI such as buttons, backgrounds, etc, the user interface elements are going to show up in Blend just fine. If however the data is fetched dynamically from a service (web, database, etc) or created dynamically, most probably Blend is going to show just an empty element. The classical way to design at that stage is to run the application, navigate to the screen that is under construction (which can involve delays, need to log in, etc…), to measure what is on the screen (colors, margins, width and height, etc) using various tools, going back to Blend, editing the properties of the elements, running again, etc. Obviously this is not ideal. The solution is to create design time data. For more information about the creation of design time data by mocking services, you can refer to two talks of mine “Deep dive MVVM” and “MVVM Applied From Silverlight to Windows Phone to Windows 8”. The source code for these talks is here and here. Design time data in MVVM Light One of the main reasons why I developed MVVM Light is to facilitate the creation of design time data. To illustrate this, let’s create a new MVVM Light application in Visual Studio. Install MVVM Light from here: http://mvvmlight.codeplex.com (use the MSI in the Download section). After installing, make sure to read the Readme that opens up in your favorite browser, you will need one more step to install the Project Templates. Start Visual Studio 2012. Create a new MvvmLight (Win8) app. Run the application. You will see a string showing “Welcome to MVVM Light”. In the Solution explorer, right click on MainPage.xaml and select Open in Blend. Now you should see “Welcome to MVVM Light [Design]” What happens here is that Expression Blend runs different code at design time than the application runs at runtime. To do this, we use design-time detection (as explained in a previous article) and use that information to initialize a different data service at design time. To understand this better, open the ViewModelLocator.cs file in the ViewModel folder and see how the DesignDataService is used at design time, while the DataService is used at runtime. In a real-life applicationm, DataService would be used to connect to a web service, for instance. When design time data fails Sometimes however, the creation of design time data fails. It can be very difficult to understand exactly what is happening. Expression Blend is not giving a lot of information about what happened. Thankfully, we can use a trick: Attaching a debugger to Expression Blend and debug the design time code. In WPF and Silverlight (including Windows Phone 7), you could simply attach the debugger to Blend.exe (using the “Managed (v4.5, v4.0) code” option even for Silverlight!!) In Windows 8 however, things are just a bit different. This is because the designer that renders the actual representation of the Windows 8 app runs in its own process. Let’s illustrate that: Open the file DesignDataService in the Design folder. Modify the GetData method to look like this: public void GetData(Action<DataItem, Exception> callback) { throw new Exception(); // Use this to create design time data var item = new DataItem("Welcome to MVVM Light [design]"); callback(item, null); } Go to Blend and build the application. The build succeeds, but now the page is empty. The creation of the design time data failed, but we don’t get a warning message. We need to investigate what’s wrong. Close MainPage.xaml Go to Visual Studio and select the menu Debug, Attach to Process. Update: Make sure that you select “Managed (v4.5, v4.0) code” in the “Attach to” field. Find the process named XDesProc.exe. You should have at least two, one for the Visual Studio 2012 designer surface, and one for Expression Blend. Unfortunately in this screen it is not obvious which is which. Let’s find out in the Task Manager. Press Ctrl-Alt-Del and select Task Manager Go to the Details tab and sort the processes by name. Find the one that says “Blend for Microsoft Visual Studio 2012 XAML UI Designer” and write down the process ID. Go back to the Attach to Process dialog in Visual Studio. sort the processes by ID and attach the debugger to the correct instance of XDesProc.exe. Open the MainViewModel (in the ViewModel folder) Place a breakpoint on the first line of the MainViewModel constructor. Go to Blend and open the MainPage.xaml again. At this point, the debugger breaks in Visual Studio and you can execute your code step by step. Simply step inside the dataservice call, and find the exception that you had placed there. Visual Studio gives you additional information which helps you to solve the issue. More info and Conclusion I want to thank the amazing people on the Expression Blend team for being very fast in guiding me in that matter and encouraging me to blog about it. More information about the XDesProc.exe process can be found here. I had to work on a Windows 8 app for a few days without design time data because of an Exception thrown somewhere in the code, and it was really painful. With the debugger, finding the issue was a simple matter of stepping into the code until it threw the exception.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Adventures in Windows 8: Placing items in a GridView with a ColumnSpan or RowSpan

    - by Laurent Bugnion
    Currently working on a Windows 8 app for an important client, I will be writing about small issues, tips and tricks, ideas and whatever occurs to me during the development and the integration of this app. When working with a GridView, it is quite common to use a VariableSizedWrapGrid as the ItemsPanel. This creates a nice flowing layout which will auto-adapt for various resolutions. This is ideal when you want to build views like the Windows 8 start menu. However immediately we notice that the Start menu allows to place items on one column (Smaller) or two columns (Larger). This switch happens through the AppBar. So how do we implement that in our app? Using ColumnSpan and RowSpan When you use a VariableSizedWrapGrid directly in your XAML, you can attach the VariableSizedWrapGrid.ColumnSpan and VariableSizedWrapGrid.RowSpan attached properties directly to an item to create the desired effect. For instance this code create this output (shown in Blend but it runs just the same): <VariableSizedWrapGrid ItemHeight="100" ItemWidth="100" Width="200" Orientation="Horizontal"> <Rectangle Fill="Purple" /> <Rectangle Fill="Orange" /> <Rectangle Fill="Yellow" VariableSizedWrapGrid.ColumnSpan="2" /> <Rectangle Fill="Red" VariableSizedWrapGrid.ColumnSpan="2" VariableSizedWrapGrid.RowSpan="2" /> <Rectangle Fill="Green" VariableSizedWrapGrid.RowSpan="2" /> <Rectangle Fill="Blue" /> <Rectangle Fill="LightGray" /> </VariableSizedWrapGrid> Using the VariableSizedWrapGrid as ItemsPanel When you use a GridView however, you typically bind the ItemsSource property to a collection, for example in a viewmodel. In that case, you want to be able to switch the ColumnSpan and RowSpan depending on properties on the item. I tried to find a way to bind the VariableSizedWrapGrid.ColumnSpan attached property on the GridView’s ItemContainerStyle template to an observable property on the item, but it didn’t work. Instead, I decided to use a StyleSelector to switch the GridViewItem’s style. Here’s how: First I added my two GridViews to my XAML as follows: <Page.Resources> <local:MainViewModel x:Key="Main" /> <DataTemplate x:Key="DataTemplate1"> <Grid Background="{Binding Brush}"> <TextBlock Text="{Binding BrushCode}" /> </Grid> </DataTemplate> </Page.Resources> <Page.DataContext> <Binding Source="{StaticResource Main}" /> </Page.DataContext> <Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}" Margin="20"> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" /> <ColumnDefinition Width="*" /> </Grid.ColumnDefinitions> <GridView ItemsSource="{Binding Items}" ItemTemplate="{StaticResource DataTemplate1}" VerticalAlignment="Top"> <GridView.ItemsPanel> <ItemsPanelTemplate> <VariableSizedWrapGrid ItemHeight="150" ItemWidth="150" /> </ItemsPanelTemplate> </GridView.ItemsPanel> </GridView> <GridView Grid.Column="1" ItemsSource="{Binding Items}" ItemTemplate="{StaticResource DataTemplate1}" VerticalAlignment="Top"> <GridView.ItemsPanel> <ItemsPanelTemplate> <VariableSizedWrapGrid ItemHeight="100" ItemWidth="100" /> </ItemsPanelTemplate> </GridView.ItemsPanel> </GridView> </Grid> The MainViewModel looks like this: public class MainViewModel { public IList<Item> Items { get; private set; } public MainViewModel() { Items = new List<Item> { new Item { Brush = new SolidColorBrush(Colors.Red) }, new Item { Brush = new SolidColorBrush(Colors.Blue) }, new Item { Brush = new SolidColorBrush(Colors.Green), }, // And more... }; } } As for the Item class, I am using an MVVM Light ObservableObject but you can use your own simple implementation of INotifyPropertyChanged of course: public class Item : ObservableObject { public const string ColSpanPropertyName = "ColSpan"; private int _colSpan = 1; public int ColSpan { get { return _colSpan; } set { Set(ColSpanPropertyName, ref _colSpan, value); } } public SolidColorBrush Brush { get; set; } public string BrushCode { get { return Brush.Color.ToString(); } } } Then I copied the GridViewItem’s style locally. To do this, I use Expression Blend’s functionality. It has the disadvantage to copy a large portion of XAML to your application, but the HUGE advantage to allow you to change the look and feel of your GridViewItem everywhere in the application. For example, you can change the selection chrome, the item’s alignments and many other properties. Actually everytime I use a ListBox, ListView or any other data control, I typically copy the item style to a resource dictionary in my application and I tweak it. Note that Blend for Windows 8 apps is automatically installed with every edition of Visual Studio 2012 (including Express) so you have no excuses anymore not to use Blend :) Open MainPage.xaml in Expression Blend by right clicking on the MainPage.xaml file in the Solution Explorer and selecting Open in Blend from the context menu. Note that the items do not look very nice! The reason is that the default ItemContainerStyle sets the content’s alignment to “Center” which I never quite understood. Seems to me that you rather want the content to be stretched, but anyway it is easy to change.   Right click on the GridView on the left and select Edit Additional Templates, Edit Generated Item Container (ItemContainerStyle), Edit a Copy. In the Create Style Resource dialog, enter the name “DefaultGridViewItemStyle”, select “Application” and press OK. Side note 1: You need to save in a global resource dictionary because later we will need to retrieve that Style from a global location. Side note 2": I would rather copy the style to an external resource dictionary that I link into the App.xaml file, but I want to keep things simple here. Blend switches in Template edit mode. The template you are editing now is inside the ItemContainerStyle and will govern the appearance of your items. This is where, for instance, the “checked” chrome is defined, and where you can alter it if you need to. Note that you can reuse this style for all your GridViews even if you use a different DataTemplate for your items. Makes sense? I probably need to think about writing another blog post dedicated to the ItemContainerStyle :) In the breadcrumb bar on top of the page, click on the style icon. The property we want to change now can be changed in the Style instead of the Template, which is a better idea. Blend is not in Style edit mode, as you can see in the Objects and Timeline pane. In the Properties pane, in the Search box, enter the word “content”. This will filter all the properties containing that partial string, including the two we are interested in: HorizontalContentAlignment and VerticalContentAlignment. Set these two values to “Stretch” instead of the default “Center”. Using the breadcrumb bar again, set the scope back to the Page (by clicking on the first crumb on the left). Notice how the items are now showing as squares in the first GridView. We will now use the same ItemContainerStyle for the second GridView. To do this, right click on the second GridView and select Edit Additional Templates, Edit Generate Item Container, Apply Resource, DefaultGridViewItemStyle. The page now looks nicer: And now for the ColumnSpan! So now, let’s change the ColumnSpan property. First, let’s define a new Style that inherits the ItemContainerStyle we created before. Make sure that you save everything in Blend by pressing Ctrl-Shift-S. Open App.xaml in Visual Studio. Below the newly created DefaultGridViewItemStyle resource, add the following style: <Style x:Key="WideGridViewItemStyle" TargetType="GridViewItem" BasedOn="{StaticResource DefaultGridViewItemStyle}"> <Setter Property="VariableSizedWrapGrid.ColumnSpan" Value="2" /> </Style> Add a new class to the project, and name it MainItemStyleSelector. Implement the class as follows: public class MainItemStyleSelector : StyleSelector { protected override Style SelectStyleCore(object item, DependencyObject container) { var i = (Item)item; if (i.ColSpan == 2) { return Application.Current.Resources["WideGridViewItemStyle"] as Style; } return Application.Current.Resources["DefaultGridViewItemStyle"] as Style; } } In MainPage.xaml, add a resource to the Page.Resources section: <local:MainItemStyleSelector x:Key="MainItemStyleSelector" /> In MainPage.xaml, replace the ItemContainerStyle property on the first GridView with the ItemContainerStyleSelector property, pointing to the StaticResource we just defined. <GridView ItemsSource="{Binding Items}" ItemTemplate="{StaticResource DataTemplate1}" VerticalAlignment="Top" ItemContainerStyleSelector="{StaticResource MainItemStyleSelector}"> <GridView.ItemsPanel> <ItemsPanelTemplate> <VariableSizedWrapGrid ItemHeight="150" ItemWidth="150" /> </ItemsPanelTemplate> </GridView.ItemsPanel> </GridView> Do the same for the second GridView as well. Finally, in the MainViewModel, change the ColumnSpan property on the 3rd Item to 2. new Item { Brush = new SolidColorBrush(Colors.Green), ColSpan = 2 }, Running the application now creates the following image, which is what we wanted. Notice how the green item is now a “wide tile”. You can also experiment by creating different Styles, all inheriting the DefaultGridViewItemStyle and using different values of RowSpan for instance. This will allow you to create any layout you want, while leaving the heavy lifting of “flowing the layout” to the GridView control. What about changing these values dynamically? Of course as we can see in the Start menu, it would be nice to be able to change the ColumnSpan and maybe even the RowSpan values at runtime. Unfortunately at this time I have not found a good way to do that. I am investigating however and will make sure to post a follow up when I find what I am looking for!   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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