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  • What is the best way to use a SSRS report viewer in a WPF application using MVVM

    - by Emad
    I have a WPF application using MVVM. I have some user controls that show some SSRS reports in a ReportViewer control hosted within a windows forms host control. The User Control has a simple combobox where the user selects a criteria and therefore the report satisfying this criteria will be loaded, its data fetched from the database and then the report is shown to the user. What is the best approach to implement such scenario in WPF using MVVM? Any samples are greatly appreciated

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  • With MVVM, does each UI window have its own ViewModel?

    - by j0rd4n
    When I'm designing multiple views under the MVVM pattern, does each view get its own ViewModel or do they all share the same one? I understand that this is ultimately a flexible decision, but what is the best practice? My gut tells me to have a ViewModel for each view (i.e. each separate UI window). All of the blog examples of MVVM show a single view but not much beyond that.

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  • Should I use ICommand or Expression.Interactions InvokeCommand for MVVM in Silverlight 4?

    - by phejndorf
    I'm about to embark on a new project in Silverlight 4, and definitely want to take advantage of the MVVM pattern, now I've finally grasped the basics. For implementing commands in Silverlight 4 it seems there are rather a lot of options ranging from the new built-in Command/ICommand option on the Button, over the InvokeCommand defined in the Microsoft.Expressions.Interactivity namespace and on to the range of assisting MVVM frameworks (Prism, MVVMlight etc). Does anyone here have gotcha's, experience and wisdom to share on this subject?

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  • MVVM in Task-It

    As I'm gearing up to write a post about dynamic XAP loading with MEF, I'd like to first talk a bit about MVVM, the Model-View-ViewModel pattern, as I will be leveraging this pattern in my future posts. Download Source Code Why MVVM? Your first question may be, "why do I need this pattern? I've been using a code-behind approach for years and it works fine." Well, you really don't have to make the switch to MVVM, but let me first explain some of the benefits I see for doing so. MVVM Benefits Testability - This is the one you'll probably hear the most about when it comes to MVVM. Moving most of the code from your code-behind to a separate view model class means you can now write unit tests against the view model without any knowledge of a view (UserControl). Multiple UIs - Let's just say that you've created a killer app, it's running in the browser, and maybe you've even made it run out-of-browser. Now what if your boss comes to you and says, "I heard about this new Windows Phone 7 device that is coming out later this year. Can you start porting the app to that device?". Well, now you have to create a new UI (UserControls, etc.) because you have a lot less screen real estate to work with. So what do you do, copy all of your existing UserControls, paste them, rename them, and then start changing the code? Hmm, that doesn't sound so good. But wait, if most of the code that makes your browser-based app tick lives in view model classes, now you can create new view (UserControls) for Windows Phone 7 that reference the same view model classes as your browser-based app. Page state - In Silverlight you're at some point going to be faced with the same issue you dealt with for years in ASP.NET, maintaining page state. Let's say a user hits your Products page, does some stuff (filters record, etc.), then leaves the page and comes back later. It would be best if the Products page was in the same state as when they left it right? Well, if you've thrown away your view (UserControl or Page) and moved off to another part of the UI, when you come back to Products you're probably going to re-instantiate your view...which will put it right back in the state it was when it started. Hmm, not good. Well, with a little help from MEF you can store the state in your view model class, MEF will keep that view model instance hanging around in memory, and then you simply rebind your view to the view model class. I made that sound easy, but it's actually a bit of work to properly store and restore the state. At least it can be done though, which will make your users a lot happier! I'll talk more about this in an upcoming blog post. No event handlers? Another nice thing about MVVM is that you can bind your UserControls to the view model, which may eliminate the need for event handlers in your code-behind. So instead of having a Click handler on a Button (or RadMenuItem), for example, you can now bind your control's Command property to a DelegateCommand in your view model (I'll talk more about Commands in an upcoming post). Instead of having a SelectionChanged event handler on your RadGridView you can now bind its SelectedItem property to a property in your view model, and each time the user clicks a row, the view model property's setter will be called. Now through the magic of binding we can eliminate the need for traditional code-behind based event handlers on our user interface controls, and the best thing is that the view model knows about everything that's going on...which means we can test things without a user interface. The brains of the operation So what we're seeing here is that the view is now just a dumb layer that binds to the view model, and that the view model is in control of just about everything, like what happens when a RadGridView row is selected, or when a RadComboBoxItem is selected, or when a RadMenuItem is clicked. It is also responsible for loading data when the page is hit, as well as kicking off data inserts, updates and deletions. Once again, all of this stuff can be tested without the need for a user interface. If the test works, then it'll work regardless of whether the user is hitting the browser-based version of your app, or the Windows Phone 7 version. Nice! The database Before running the code for this app you will need to create the database. First, create a database called MVVMProject in SQL Server, then run MVVMProject.sql in the MVVMProject/Database directory of your downloaded .zip file. This should give you a Task table with 3 records in it. When you fire up the solution you will also need to update the connection string in web.config to point to your database instead of IBM12\SQLSERVER2008. The code One note about this code is that it runs against the latest Silverlight 4 RC and WCF RIA Services code. Please see my first blog post about updating to the RC bits. Beta to RC - Part 1 At the top of this post is a link to a sample project that demonstrates a sample application with a Tasks page that uses the MVVM pattern. This is a simplified version of how I have implemented the Tasks page in the Task-It application. Youll notice that Tasks.xaml has very little code to it. Just a TextBlock that displays the page title and a ContentControl. <StackPanel>     <TextBlock Text="Tasks" Style="{StaticResource PageTitleStyle}"/>     <Rectangle Style="{StaticResource StandardSpacerStyle}"/>     <ContentControl x:Name="ContentControl1"/> </StackPanel> In List.xaml we have a RadGridView. Notice that the ItemsSource is bound to a property in the view model class call Tasks, SelectedItem is bound to a property in the view model called SelectedItem, and IsBusy is bound to a property in the view model called IsLoading. <Grid>     <telerikGridView:RadGridView ItemsSource="{Binding Tasks}" SelectedItem="{Binding SelectedItem, Mode=TwoWay}"                                  IsBusy="{Binding IsLoading}" AutoGenerateColumns="False" IsReadOnly="True" RowIndicatorVisibility="Collapsed"                IsFilteringAllowed="False" ShowGroupPanel="False">         <telerikGridView:RadGridView.Columns>             <telerikGridView:GridViewDataColumn Header="Name" DataMemberBinding="{Binding Name}" Width="3*"/>             <telerikGridView:GridViewDataColumn Header="Due" DataMemberBinding="{Binding DueDate}" DataFormatString="{}{0:d}" Width="*"/>         </telerikGridView:RadGridView.Columns>     </telerikGridView:RadGridView> </Grid> In Details.xaml we have a Save button that is bound to a property called SaveCommand in our view model. We also have a simple form (Im using a couple of controls here from Silverlight.FX for the form layout, FormPanel and Label simply because they make for a clean XAML layout). Notice that the FormPanel is also bound to the SelectedItem in the view model (the same one that the RadGridView is). The two form controls, the TextBox and RadDatePicker) are bound to the SelectedItem's Name and DueDate properties. These are properties of the Task object that WCF RIA Services creates. <StackPanel>     <Button Content="Save" Command="{Binding SaveCommand}" HorizontalAlignment="Left"/>     <Rectangle Style="{StaticResource StandardSpacerStyle}"/>     <fxui:FormPanel DataContext="{Binding SelectedItem}" Style="{StaticResource FormContainerStyle}">         <fxui:Label Text="Name:"/>         <TextBox Text="{Binding Name, Mode=TwoWay}"/>         <fxui:Label Text="Due:"/>         <telerikInput:RadDatePicker SelectedDate="{Binding DueDate, Mode=TwoWay}"/>     </fxui:FormPanel> </StackPanel> In the code-behind of the Tasks control, Tasks.xaml.cs, I created an instance of the view model class (TasksViewModel) in the constructor and set it as the DataContext for the control. The Tasks page will load one of two child UserControls depending on whether you are viewing the list of tasks (List.xaml) or the form for editing a task (Details.xaml). // Set the DataContext to an instance of the view model class var viewModel = new TasksViewModel(); DataContext = viewModel;   // Child user controls (inherit DataContext from this user control) List = new List(); // RadGridView Details = new Details(); // Form When the page first loads, the List is loaded into the ContentControl. // Show the RadGridView first ContentControl1.Content = List; In the code-behind we also listen for a couple of the view models events. The ItemSelected event will be fired when the user clicks on a record in the RadGridView in the List control. The SaveCompleted event will be fired when the user clicks Save in the Details control (the form). Here the view model is in control, and is letting the view know when something needs to change. // Listeners for the view model's events viewModel.ItemSelected += OnItemSelected; viewModel.SaveCompleted += OnSaveCompleted; The event handlers toggle the view between the RadGridView (List) and the form (Details). void OnItemSelected(object sender, RoutedEventArgs e) {     // Show the form     ContentControl1.Content = Details; }   void OnSaveCompleted(object sender, RoutedEventArgs e) {     // Show the RadGridView     ContentControl1.Content = List; } In TasksViewModel, we instantiate a DataContext object and a SaveCommand in the constructor. DataContext is a WCF RIA Services object that well use to retrieve the list of Tasks and to save any changes to a task. Ill talk more about this and Commands in future post, but for now think of the SaveCommand as an event handler that is called when the Save button in the form is clicked. DataContext = new DataContext(); SaveCommand = new DelegateCommand(OnSave); When the TasksViewModel constructor is called we also make a call to LoadTasks. This sets IsLoading to true (which causes the RadGridViews busy indicator to appear) and retrieves the records via WCF RIA Services.         public LoadOperation<Task> LoadTasks()         {             // Show the loading message             IsLoading = true;             // Get the data via WCF RIA Services. When the call has returned, called OnTasksLoaded.             return DataContext.Load(DataContext.GetTasksQuery(), OnTasksLoaded, false);         } When the data is returned, OnTasksLoaded is called. This sets IsLoading to false (which hides the RadGridViews busy indicator), and fires property changed notifications to the UI to let it know that the IsLoading and Tasks properties have changed. This property changed notification basically tells the UI to rebind. void OnTasksLoaded(LoadOperation<Task> lo) {     // Hide the loading message     IsLoading = false;       // Notify the UI that Tasks and IsLoading properties have changed     this.OnPropertyChanged(p => p.Tasks);     this.OnPropertyChanged(p => p.IsLoading); } Next lets look at the view models SelectedItem property. This is the one thats bound to both the RadGridView and the form. When the user clicks a record in the RadGridView its setter gets called (set a breakpoint and see what I mean). The other code in the setter lets the UI know that the SelectedItem has changed (so the form displays the correct data), and fires the event that notifies the UI that a selection has occurred (which tells the UI to switch from List to Details). public Task SelectedItem {     get { return _selectedItem; }     set     {         _selectedItem = value;           // Let the UI know that the SelectedItem has changed (forces it to re-bind)         this.OnPropertyChanged(p => p.SelectedItem);         // Notify the UI, so it can switch to the Details (form) page         NotifyItemSelected();     } } One last thing, saving the data. When the Save button in the form is clicked it fires the SaveCommand, which calls the OnSave method in the view model (once again, set a breakpoint to see it in action). public void OnSave() {     // Save the changes via WCF RIA Services. When the save is complete, call OnSaveCompleted.     DataContext.SubmitChanges(OnSaveCompleted, null); } In OnSave, we tell WCF RIA Services to submit any changes, which there will be if you changed either the Name or the Due Date in the form. When the save is completed, it calls OnSaveCompleted. This method fires a notification back to the UI that the save is completed, which causes the RadGridView (List) to show again. public virtual void OnSaveCompleted(SubmitOperation so) {     // Clear the item that is selected in the grid (in case we want to select it again)     SelectedItem = null;     // Notify the UI, so it can switch back to the List (RadGridView) page     NotifySaveCompleted(); } 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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  • Connect Team Foundation Service/TFS 2012 with Visual Studio 2010 &amp; Visual Studio 2008

    - by Vishal
    Hello, Microsoft finally released the Team Foundation Service in late October 2012 after its long time in the preview phase. I was already using the TFS Preview which was free but I was happy to see Microsoft releasing the Team Foundation Service also FREE for upto 5 users. Isn't that great news? I know there are bunch of other free source control repositories (Github, Bitbucket, SVN etc.) out there but I somehow like TFS better. Also the other good thing about the final release was that I didn’t had to do any kind of migration of my code from preview to final release version. Just changed the TFS connection URL and it worked like a charm. Anyways, if you are a startup with small team and need some awesome Source Control along with all the good Project Management, Continuous Integration (Build, Test, Deploy), Team Collaboration, Agile/Scrum planning etc. features than Team Foundation Service is your answer. Microsoft has not yet released their pricing for more than 5 users and will be releasing it sometime in early 2013. What if as of now you have a team more than 5 users and you want to use Team Foundation Service, the good news is you can use it for FREE but when they release the final pricing, you will have to transition to the paid plan. Lot of story, getting to the point, connecting to Team Foundation Service with Visual Studio 2012 is straight forward and would work out of the box but it wont for previous versions of Visual Studio. You will have to upgrade to the latest service pack first and than install the forward compatibility pack. (1st : Service Packs & 2nd: Forward Compatibility packs) For Visual Studio 2010: Visual Studio 2010 Service Pack 1. Visual Studio 2010 forward compatibility for TFS 2012 and Team Foundation Service.         For Visual Studio 2008: Visual Studio 2008 Service Pack 1. Visual Studio 2008 forward compatibility for TFS 2012 & Team Foundation Service. Restart your system. Visual Studio 2008 will not work if you only put https://xxx.visualstudio.com. You will have to put your collection name too as shown below.       By the way, it doesn’t matter if you are an Apple Application Developer or Android App Developer, you can still use Team Foundation Service as your source control. Below are few links to connect to Team Foundation Service with other IDEs: Connect Eclipse to Team Foundation Service. Connect XCode to Team Foundation Service. Happy coding. Vishal Mody

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  • JavaScript Data Binding Frameworks

    - by dwahlin
    Data binding is where it’s at now days when it comes to building client-centric Web applications. Developers experienced with desktop frameworks like WPF or web frameworks like ASP.NET, Silverlight, or others are used to being able to take model objects containing data and bind them to UI controls quickly and easily. When moving to client-side Web development the data binding story hasn’t been great since neither HTML nor JavaScript natively support data binding. This means that you have to write code to place data in a control and write code to extract it. Although it’s certainly feasible to do it from scratch (many of us have done it this way for years), it’s definitely tedious and not exactly the best solution when it comes to maintenance and re-use. Over the last few years several different script libraries have been released to simply the process of binding data to HTML controls. In fact, the subject of data binding is becoming so popular that it seems like a new script library is being released nearly every week. Many of the libraries provide MVC/MVVM pattern support in client-side JavaScript apps and some even integrate directly with server frameworks like Node.js. Here’s a quick list of a few of the available libraries that support data binding (if you like any others please add a comment and I’ll try to keep the list updated): AngularJS MVC framework for data binding (although closely follows the MVVM pattern). Backbone.js MVC framework with support for models, key/value binding, custom events, and more. Derby Provides a real-time environment that runs in the browser an in Node.js. The library supports data binding and templates. Ember Provides support for templates that automatically update as data changes. JsViews Data binding framework that provides “interactive data-driven views built on top of JsRender templates”. jQXB Expression Binder Lightweight jQuery plugin that supports bi-directional data binding support. KnockoutJS MVVM framework with robust support for data binding. For an excellent look at using KnockoutJS check out John Papa’s course on Pluralsight. Meteor End to end framework that uses Node.js on the server and provides support for data binding on  the client. Simpli5 JavaScript framework that provides support for two-way data binding. WinRT with HTML5/JavaScript If you’re building Windows 8 applications using HTML5 and JavaScript there’s built-in support for data binding in the WinJS library.   I won’t have time to write about each of these frameworks, but in the next post I’m going to talk about my (current) favorite when it comes to client-side JavaScript data binding libraries which is AngularJS. AngularJS provides an extremely clean way – in my opinion - to extend HTML syntax to support data binding while keeping model objects (the objects that hold the data) free from custom framework method calls or other weirdness. While I’m writing up the next post, feel free to visit the AngularJS developer guide if you’d like additional details about the API and want to get started using it.

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  • Tales from the Trenches – Building a Real-World Silverlight Line of Business Application

    - by dwahlin
    There's rarely a boring day working in the world of software development. Part of the fun associated with being a developer is that change is guaranteed and the more you learn about a particular technology the more you realize there's always a different or better way to perform a task. I've had the opportunity to work on several different real-world Silverlight Line of Business (LOB) applications over the past few years and wanted to put together a list of some of the key things I've learned as well as key problems I've encountered and resolved. There are several different topics I could cover related to "lessons learned" (some of them were more painful than others) but I'll keep it to 5 items for this post and cover additional lessons learned in the future. The topics discussed were put together for a TechEd talk: Pick a Pattern and Stick To It Data Binding and Nested Controls Notify Users of Successes (and failures) Get an Agent – A Service Agent Extend Existing Controls The first topic covered relates to architecture best practices and how the MVVM pattern can save you time in the long run. When I was first introduced to MVVM I thought it was a lot of work for very little payoff. I've since learned (the hard way in some cases) that my initial impressions were dead wrong and that my criticisms of the pattern were generally caused by doing things the wrong way. In addition to MVVM pros the slides and sample app below also jump into data binding tricks in nested control scenarios and discuss how animations and media can be used to enhance LOB applications in subtle ways. Finally, a discussion of creating a re-usable service agent to interact with backend services is discussed as well as how existing controls make good candidates for customization. I tried to keep the samples simple while still covering the topics as much as possible so if you’re new to Silverlight you should definitely be able to follow along with a little study and practice. I’d recommend starting with the SilverlightDemos.View project, moving to the SilverlightDemos.ViewModels project and then going to the SilverlightDemos.ServiceAgents project. All of the backend “Model” code can be found in the SilverlightDemos.Web project. Custom controls used in the app can be found in the SivlerlightDemos.Controls project.   Sample Code and Slides

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  • Attached Property port of my Window Close Behavior

    - by Reed
    Nishant Sivakumar just posted a nice article on The Code Project.  It is a port of the MVVM-friendly Blend Behavior I wrote about in a previous article to WPF using Attached Properties. While similar to the WindowCloseBehavior code I posted on the Expression Code Gallery, Nishant Sivakumar’s version works in WPF without taking a dependency on the Expression Blend SDK. I highly recommend reading this article: Handling a Window’s Closed and Closing Events in the View-Model.  It is a very nice alternative approach to this common problem in MVVM.

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  • How have you successfully implemented MessageBox.Show() functionality in MVVM?

    - by Edward Tanguay
    I've got a WPF application which calls MessageBox.Show() way back in the ViewModel (to check if the user really wants to delete). This actually works, but goes against the grain of MVVM since the ViewModel should not explicitly determine what happens on the View. So now I am thinking how can I best implement the MessageBox.Show() functionality in my MVVM application, options: I could have a message with the text "Are you sure...?" along with two buttons Yes and No all in a Border in my XAML, and create a trigger on the template so that it is collapsed/visible based on a ViewModelProperty called AreYourSureDialogueBoxIsVisible, and then when I need this dialogue box, assign AreYourSureDialogueBoxIsVisible to "true", and also handle the two buttons via DelegateCommand back in my ViewModel. I could also somehow try to handle this with triggers in XAML so that the Delete button actually just makes some Border element appear with the message and buttons in it, and the Yes button did the actually deleting. Both solutions seem to be too complex for what used to be a couple lines of code with MessageBox.Show(). In what ways have you successfully implemented Dialogue Boxes in your MVVM applications?

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  • MVVM Project and Item Templates

    - by Timmy Kokke
    Intro This is the first in a series of small articles about what is new in Silverlight 4 and Expression Blend 4. The series is build around a open source demo application SilverAmp which is available on http://SilverAmp.CodePlex.com.   MVVM Project and Item Templates Expression Blend has got a new project template to get started with a Model-View-ViewModel project  easily. The template provides you with a View and a ViewModel bound together. It also adds the ViewModel to the SampleData of your project. It is available for both Silverlight and Wpf. To get going, start a new project in Expression Blend and select Silverlight DataBound Application from the Silverlight project type. In this case I named the project DemoTest1. The solution now contains several folders: SampleData; which contains a data to show in Blend ViewModels; starts with one file, MainViewModel.cs Views; containing MainView.xaml with codebehind used for binding with the MainViewModel class. and your regular App.xaml and MainPage.xaml The MainViewModel class contains a sample property and a sample method. Both the property and the method are used in the MainView control. The MainView control is a regular UserControl and is placed in the MainPage. You can continue on building your applicaition by adding your own properties and methods to the ViewModel and adding controls to the View. Adding Views with ViewModels is very easy too. The guys at Microsoft where nice enough to add a new Item template too: a UserControl with ViewModel. If you add this new item to the root of your solution it will add the .xaml file to the views folder and a .cs file to the ViewModels folder. Conclusion The databound Application project type is a great to get your MVVM based project started. It also functions a great source of information about how to connect it all together.   Technorati Tags: Silverlight,Wpf,Expression Blend,MVVM

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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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  • TechEd 2012: MVVM In XAML

    - by Tim Murphy
    Paul Sheriff was a real character at the start of his MVVM in XAML session.  There was a lot of sarcasm and self deprecation going on prior to the .  That is never a bad way to get things rolling right after lunch.  Then things got semi-serious. The presentation itself had a number of surprises, but not all of them had to do with XAML.  When he flipped over his company’s code generation tool it took me off guard.  I am used to generator that create code for a whole project, but his tools were able to create different types of constructs on demand.  It also made it easier to follow what he was doing than some of the other demos I have seen this week where people were using code snippets. Getting to the heart of the topic I found myself thinking that I may have found my utopia for application development in MVVM.  Yes, I know there is no such thing, but this comes closer than any other pattern I have learned about.  This pattern allows the application to have better separation of concerns than I have seen before.  This is especially true since you can leverage data binding.  I’m not sure why it has taken me so long to find time for this subject. As Paul demonstrated using this pattern with XAML gives you multi-platform reusable code when you leverage common utility classes and ModelView classes.  The one drawback I see is that you have to go to the lowest common denominator between the platforms you want to support, but you always have to weigh the trade offs. And finally, the Visual Studio nuggets just keep coming.  Even though it has been available for several generations of Visual Studio I have never seen someone use linked files within a solution.  It just goes to show that I should spend more time exploring the deeper features of each dialog. del.icio.us Tags: TechEd,TechEd 2012,MVVM,Paul Sheriff,Patterns,Visual Studio 2012

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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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  • Free Team Foundation Service a Boon for Play Projects

    - by Ken Cox [MVP]
    My ‘jump in and sink or swim’ learning style leads me to create dozens of unbillable ‘play’ projects in Visual Studio 2012.  For example, I’m currently learning to customize the powerful auction/fixed price/classifieds software called AuctionWorx Enterprise.  I make stupid mistakes as I grasp a new API and configure projects. It’s frustrating to go down a rat hole and discover the VS IDE’s Undo doesn’t reach back to a working build from the previous weekend. Enter Visual Studio’s Free Team Foundation Service.  Put your play projects into the free source control and check in (or shelve) a snapshot before embarking on something risky. (I already use Discount ASP.NET’s Team Foundation Server hosting for client projects so there’s zero TFS/VS learning curve for me and first class GUI support.) TFS is free right now for teams of five or fewer. I’m not naive enough to expect ‘free’ to last forever. So, it’ll be interesting to see how much Microsoft intends to charge in 2013 for TFS. In the meantime, why not grab some free source code storage? BTW, it’s weird to realize that Microsoft is backing up my junky little playtime code on three physically-distinct servers every day - and taking incremental backups every hour.

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  • Team Foundation Service Preview now open for all!

    - by Tarun Arora
    The concept of TFS in the cloud was first presented back in early 2010, the product team worked hard to preview a constantly evolving solution at the BUILD conference last year and after having completed 31 Sprints today the preview service has been opened for all. No more invitation codes required, TfsPreview has been made public! “Since we announced the Team Foundation Service Preview at the BUILD conference last year, we’ve limited the on boarding of new customers by requiring invitation codes to create accounts.  The main reason for this has been to control the growth of the service to make sure it didn’t run away from us and end up with a bad user experience.  In this time period, we’ve continued to work on our infrastructure, performance, scale, monitoring, management and, of course, some cool new features like cloud build. ”   - Brian Harry Since the service is still in preview, it is free for all… If you haven’t, now is the best time to try out the offering. There is no fixed time line on how long before service becomes chargeable but the terms of service support production use, the service is reliable and the product team committed to carry all of your data forward into production. “The service will remain in “preview” for a while longer while we work through additional features like data portability, commercial terms, etc but the terms of service support production use, the service is reliable and we expect to carry all of your data forward into production. ”  - Brian Harry As of today it’s possible to use TFS Preview with VS 2012 RC, VS 2010 SP1, VS 2008 SP1, the service currently does not work with VS 2005, this is something the product team is actively working on. You can refer to Brian’s announcement blog post here, http://blogs.msdn.com/b/bharry/archive/2012/06/11/team-foundation-service-preview-is-public.aspx

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  • Configuring Team Foundation Server Basic on Home Server.

    - by Enrique Lima
    For the installation I selected only the Team Foundation Server role. Then, I opened the Team Foundation Server Administration Console (which I think is a great addition and improvement over the way TFS was configured in the past) to proceed with the configuration of the pieces. Once I selected the Configure Installed Features, the Configuration Center opened up. Now, the choices … In my implementation here I just want to take advantage of Source Control primarily.  I want to be able to store my code and projects.  So, Basic it is! So, the Basic Configuration Wizard opens up.  Now the options to configure are very limited, but we have to provide details for the SQL Server Instance. And now, to select Install SQL Server express.  If you want to take advantage of another system in your environment to host your database, well you could Use an existing SQL Server Instance. Once it has the details it needs, you get a Summary view to confirm your choices. Once, you click next or verify, it runs readiness checks on your system to make sure the installation will have a successful pass.  And we love GREEN! Now, since got the green flag, our next stop is to let the wizard do its magic, click on Configure.  And once again, we love GREEN! We click Next, and … We like a big Green Success sign … We close the Configuration Center … First results … Web Access …  Nothing to show … but we are there! And all this running from a Microsoft Home Server installation.

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  • The last MVVM you'll ever need?

    - by Nuri Halperin
    As my MVC projects mature and grow, the need to have some omnipresent, ambient model properties quickly emerge. The application no longer has only one dynamic pieced of data on the page: A sidebar with a shopping cart, some news flash on the side – pretty common stuff. The rub is that a controller is invoked in context of a single intended request. The rest of the data, even though it could be just as dynamic, is expected to appear on it's own. There are many solutions to this scenario. MVVM prescribes creating elaborate objects which expose your new data as a property on some uber-object with more properties exposing the "side show" ambient data. The reason I don't love this approach is because it forces fairly acute awareness of the view, and soon enough you have many MVVM objects laying around, and views have to start doing null-checks in order to ensure you really supplied all the values before binding to them. Ick. Just as unattractive is the ViewData dictionary. It's not strongly typed, and in both this and the MVVM approach someone has to populate these properties – n'est pas? Where does that live? With MVC2, we get the formerly-futures  feature Html.RenderAction(). The feature allows you plant a line in a view, of the format: <% Html.RenderAction("SessionInterest", "Session"); %> While this syntax looks very clean, I can't help being bothered by it. MVC was touting a very strong separation of concerns, the Model taking on the role of the business logic, the controller handling route and performing minimal view-choosing operations and the views strictly focused on rendering out angled-bracket tags. The RenderAction() syntax has the view calling some controller and invoking it inline with it's runtime rendering. This – to my taste – embeds too much  knowledge of controllers into the view's code – which was allegedly forbidden.  The one way flow "Controller Receive Data –> Controller invoke Model –> Controller select view –> Controller Hand data to view" now gets a "View calls controller and gets it's own data" which is not so one-way anymore. Ick. I toyed with some other solutions a bit, including some base controllers, special view classes etc. My current favorite though is making use of the ExpandoObject and dynamic features with C# 4.0. If you follow Phil Haack or read a bit from David Heyden you can see the general picture emerging. The game changer is that using the new dynamic syntax, one can sprout properties on an object and make use of them in the view. Well that beats having a bunch of uni-purpose MVVM's any day! Rather than statically exposed properties, we'll just use the capability of adding members at runtime. Armed with new ideas and syntax, I went to work: First, I created a factory method to enrich the focuse object: public static class ModelExtension { public static dynamic Decorate(this Controller controller, object mainValue) { dynamic result = new ExpandoObject(); result.Value = mainValue; result.SessionInterest = CodeCampBL.SessoinInterest(); result.TagUsage = CodeCampBL.TagUsage(); return result; } } This gives me a nice fluent way to have the controller add the rest of the ambient "side show" items (SessionInterest, TagUsage in this demo) and expose them all as the Model: public ActionResult Index() { var data = SyndicationBL.Refresh(TWEET_SOURCE_URL); dynamic result = this.Decorate(data); return View(result); } So now what remains is that my view knows to expect a dynamic object (rather than statically typed) so that the ASP.NET page compiler won't barf: <%@ Page Language="C#" Title="Ambient Demo" MasterPageFile="~/Views/Shared/Ambient.Master" Inherits="System.Web.Mvc.ViewPage<dynamic>" %> Notice the generic ViewPage<dynamic>. It doesn't work otherwise. In the page itself, Model.Value property contains the main data returned from the controller. The nice thing about this, is that the master page (Ambient.Master) also inherits from the generic ViewMasterPage<dynamic>. So rather than the page worrying about all this ambient stuff, the side bars and panels for ambient data all reside in a master page, and can be rendered using the RenderPartial() syntax: <% Html.RenderPartial("TagCloud", Model.SessionInterest as Dictionary<string, int>); %> Note here that a cast is necessary. This is because although dynamic is magic, it can't figure out what type this property is, and wants you to give it a type so its binder can figure out the right property to bind to at runtime. I use as, you can cast if you like. So there we go – no violation of MVC, no explosion of MVVM models and voila – right? Well, I could not let this go without a tweak or two more. The first thing to improve, is that some views may not need all the properties. In that case, it would be a waste of resources to populate every property. The solution to this is simple: rather than exposing properties, I change d the factory method to expose lambdas - Func<T> really. So only if and when a view accesses a member of the dynamic object does it load the data. public static class ModelExtension { // take two.. lazy loading! public static dynamic LazyDecorate(this Controller c, object mainValue) { dynamic result = new ExpandoObject(); result.Value = mainValue; result.SessionInterest = new Func<Dictionary<string, int>>(() => CodeCampBL.SessoinInterest()); result.TagUsage = new Func<Dictionary<string, int>>(() => CodeCampBL.TagUsage()); return result; } } Now that lazy loading is in place, there's really no reason not to hook up all and any possible ambient property. Go nuts! Add them all in – they won't get invoked unless used. This now requires changing the signature of usage on the ambient properties methods –adding some parenthesis to the master view: <% Html.RenderPartial("TagCloud", Model.SessionInterest() as Dictionary<string, int>); %> And, of course, the controller needs to call LazyDecorate() rather than the old Decorate(). The final touch is to introduce a convenience method to the my Controller class , so that the tedium of calling Decorate() everywhere goes away. This is done quite simply by adding a bunch of methods, matching View(object), View(string,object) signatures of the Controller class: public ActionResult Index() { var data = SyndicationBL.Refresh(TWEET_SOURCE_URL); return AmbientView(data); } //these methods can reside in a base controller for the solution: public ViewResult AmbientView(dynamic data) { dynamic result = ModelExtension.LazyDecorate(this, data); return View(result); } public ViewResult AmbientView(string viewName, dynamic data) { dynamic result = ModelExtension.LazyDecorate(this, data); return View(viewName, result); } The call to AmbientView now replaces any call the View() that requires the ambient data. DRY sattisfied, lazy loading and no need to replace core pieces of the MVC pipeline. I call this a good MVC day. Enjoy!

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  • How are views constructed in Josh Smith's MVVM sample?

    - by Wim Coenen
    Being new to both WPF and MVVM, I'm studying Josh Smith's article on the MVVM pattern and the accompanying sample code. I can see that the application is started in app.xaml.cs by constructing a MainWindow object, wiring it to a MainWindowViewModel object and then showing the main window. So far so good. However, I can't find any code which instantiates the AllCustomersView or CustomerView classes. Using "find all references" on the constructors of those views comes up with nothing. What am I missing here?

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  • Why are events and commands in MVVM so unsupported by WPF / Visual Studio?

    - by Edward Tanguay
    When creating an WPF application with the MVVM pattern, it seems I have to gather the necessary tools myself to even begin the most rudimentary event handling, e.g. AttachedBehaviors I get from here DelegateCommands I get from here Now I'm looking for some way to handle the ItemSelected event in a ComboBox and am getting suggestions of tricks and workarounds to do this (using a XAML trigger or have other elements bound to the selected item, etc.). Ok, I can go down this road, but it seems to be reinventing the wheel. It would be nice to just have an ItemSelected command that I can handle in my ViewModel. Am I missing some set of standard tools or is everyone doing MVVM with WPF basically building and putting together their own collection of tools just so they can do the simplest plumbing tasks with events and commands, things that take only a couple lines in code-behind with a Click="eventHandler"?

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  • Why are events and commands in MVVM so unsupported by WPF / Visual Studio?

    - by Edward Tanguay
    When creating an WPF application with the MVVM pattern, it seems I have to gather the necessary tools myself to even begin the most rudimentary event handling, e.g. AttachedBehaviors I get from here DelegateCommands I get from here Now I'm looking for some way to handle the ItemSelected event in a ComboBox and am getting suggestions of tricks and workarounds to do this (using a XAML trigger or have other elements bound to the selected item, etc.). Ok, I can go down this road, but it seems to be reinventing the wheel. It would be nice to just have an ItemSelected command that I can handle in my ViewModel. Am I missing some set of standard tools or is everyone doing MVVM with WPF basically building and putting together their own collection of tools just so they can do the simplest plumbing tasks with events and commands, things that take only a couple lines in code-behind with a Click="eventHandler"?

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