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  • How do I MVVM-ize this MouseDown code in my WPF 3D app?

    - by DanM
    In my view, I have: <UserControl x:Class ... MouseDown="UserControl_MouseDown"> <Viewport3D Name="Viewport" Grid.Column="0"> ... </Viewport3D > </UserControl> In my code-behind, I have: private void UserControl_MouseDown(object sender, MouseButtonEventArgs e) { ((MapPanelViewModel)DataContext).OnMouseDown(e, Viewport); } And in my view-model, I have: public void OnMouseDown(MouseEventArgs e, Viewport3D viewport) { var range = new LineRange(); var isValid = ViewportInfo.Point2DtoPoint3D(viewport, e.GetPosition(viewport), out range); if (!isValid) MouseCoordinates = "(no data)"; else { var point3D = range.PointFromZ(0); var point = ViewportInfo.Point3DtoPoint2D(viewport, point3D); MouseCoordinates = e.GetPosition(viewport).ToString() + "\n" + point3D + "\n" + point; } } I really don't have a good sense of how to handle mouse events with MVVM. I always just end up putting them in the code-behind and casting the DataContext as SomeViewModel, then passing the MouseEventArgs on to a handler in my view-model. That's bad enough already, but in this case, I'm actually passing in a control (a Viewport3D), which is necessary for translating coordinates between 2D and 3D. Any suggestions on how to make this more in tune with MVVM?

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  • MVVM: Do I need Inheritance with ViewModels A + B ?

    - by Lisa
    Hello guys my first post on SO because EE sucks in the meantime ;P I am using wpf and mvvm in my desktop application. Scenario: I have a calendar with week A and week B which are rotating by every X week depending on the user settings. But the UserControl "week B" is only visible when the user sets the option "rotating weeks"... The UserControl with week A has a DataGrid and for week B I want to use the same UserControl of course. What I want to achieve is that all data entered/choosen by the user in the Week A is saved/backed by a ViewModel A and Model C. When the user wants a rotating weekly calendar plan I need also a ViewModel B and again Model C. The reason why I need to know what data entered by the user belongs to week A or week B is because I have to write the entered data in a certain order into the database = db.Write(weekA),db.Write(weekB),db.Write(weekA),etc... I am unsure how a solution could look like... What would you do to identify a ViewModel A or B so you know the order of how to write the data in the proper order into database? Any other suggestions are also welcome of course, maybe I think in the wrong direction its late here :) I am new to mvvm so please be patient.

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  • Big smart ViewModels, dumb Views, and any model, the best MVVM approach?

    - by Edward Tanguay
    The following code is a refactoring of my previous MVVM approach (Fat Models, skinny ViewModels and dumb Views, the best MVVM approach?) in which I moved the logic and INotifyPropertyChanged implementation from the model back up into the ViewModel. This makes more sense, since as was pointed out, you often you have to use models that you either can't change or don't want to change and so your MVVM approach should be able to work with any model class as it happens to exist. This example still allows you to view the live data from your model in design mode in Visual Studio and Expression Blend which I think is significant since you could have a mock data store that the designer connects to which has e.g. the smallest and largest strings that the UI can possibly encounter so that he can adjust the design based on those extremes. Questions: I'm a bit surprised that I even have to "put a timer" in my ViewModel since it seems like that is a function of INotifyPropertyChanged, it seems redundant, but it was the only way I could get the XAML UI to constantly (once per second) reflect the state of my model. So it would be interesting to hear anyone who may have taken this approach if you encountered any disadvantages down the road, e.g. with threading or performance. The following code will work if you just copy the XAML and code behind into a new WPF project. XAML: <Window x:Class="TestMvvm73892.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:TestMvvm73892" Title="Window1" Height="300" Width="300"> <Window.Resources> <ObjectDataProvider x:Key="DataSourceCustomer" ObjectType="{x:Type local:CustomerViewModel}" MethodName="GetCustomerViewModel"/> </Window.Resources> <DockPanel DataContext="{StaticResource DataSourceCustomer}"> <StackPanel DockPanel.Dock="Top" Orientation="Horizontal"> <TextBlock Text="{Binding Path=FirstName}"/> <TextBlock Text=" "/> <TextBlock Text="{Binding Path=LastName}"/> </StackPanel> <StackPanel DockPanel.Dock="Top" Orientation="Horizontal"> <TextBlock Text="{Binding Path=TimeOfMostRecentActivity}"/> </StackPanel> </DockPanel> </Window> Code Behind: using System; using System.Windows; using System.ComponentModel; using System.Threading; namespace TestMvvm73892 { public partial class Window1 : Window { public Window1() { InitializeComponent(); } } //view model public class CustomerViewModel : INotifyPropertyChanged { private string _firstName; private string _lastName; private DateTime _timeOfMostRecentActivity; private Timer _timer; public string FirstName { get { return _firstName; } set { _firstName = value; this.RaisePropertyChanged("FirstName"); } } public string LastName { get { return _lastName; } set { _lastName = value; this.RaisePropertyChanged("LastName"); } } public DateTime TimeOfMostRecentActivity { get { return _timeOfMostRecentActivity; } set { _timeOfMostRecentActivity = value; this.RaisePropertyChanged("TimeOfMostRecentActivity"); } } public CustomerViewModel() { _timer = new Timer(CheckForChangesInModel, null, 0, 1000); } private void CheckForChangesInModel(object state) { Customer currentCustomer = CustomerViewModel.GetCurrentCustomer(); MapFieldsFromModeltoViewModel(currentCustomer, this); } public static CustomerViewModel GetCustomerViewModel() { CustomerViewModel customerViewModel = new CustomerViewModel(); Customer currentCustomer = CustomerViewModel.GetCurrentCustomer(); MapFieldsFromModeltoViewModel(currentCustomer, customerViewModel); return customerViewModel; } public static void MapFieldsFromModeltoViewModel(Customer model, CustomerViewModel viewModel) { viewModel.FirstName = model.FirstName; viewModel.LastName = model.LastName; viewModel.TimeOfMostRecentActivity = model.TimeOfMostRecentActivity; } public static Customer GetCurrentCustomer() { return Customer.GetCurrentCustomer(); } //INotifyPropertyChanged implementation public event PropertyChangedEventHandler PropertyChanged; private void RaisePropertyChanged(string property) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(property)); } } } //model public class Customer { public string FirstName { get; set; } public string LastName { get; set; } public DateTime TimeOfMostRecentActivity { get; set; } public static Customer GetCurrentCustomer() { return new Customer { FirstName = "Jim", LastName = "Smith", TimeOfMostRecentActivity = DateTime.Now }; } } }

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  • Examples of different architecture methodologies

    - by Lane
    Is there a resource or site which illustrates building the same application (desktop or web) using several different contrasting architectures? Such as MVP versus MVVM versus MVC, etc. It would be very helpful to see how they look side-by-side using real-world code instead of comparing written theory to written theory. I've often found that something can be described well in a book, but when you go to implement it, the subtleties and weaknesses of the theory become readily apparent.

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  • How can we implement change notification propagation for WPF and SL in the MVVM pattern?

    - by Firoso
    Here's an example scenario targetting MVVM WPF/SL development: View data binds to view model Property "Target" "Target" exposes a field of an object called "data" that exists in the local application model, called "Original" when "Original" changes, it should raise notification to the view model and then propogate that change notification to the View. Here are the solutions I've come up with, but I don't like any of them all that much. I'm looking for other ideas, by the time we come up with something rock solid I'm certain Microsoft will have released .NET 5 with WPF/SL extensions for better tools for MVVM development. For now the question is, "What have you done to solve this problem and how has it worked out for you?" Option 1. Proposal: Attach a handler to data's PropertyChanged event that watches for string values of properties it cares about that might have changed, and raises the appropriate notification. Why I don't like it: Changes don't bubble naturally, objects must be explicitly watched, if data changes to a new source, events must be un-registered/registered. Why I kind of like it: I get explicit control over propogation of changes, and I don't have to use any types that belong at a higher level of the application such as dependancy properties. Option 2. Proposal: Attach a handler to data's PropertyChanged event that re-raises the event across all properties using the name property name. Why I don't like it: This is essentially the same as option 1, but less intelligent, and forces me to never change my property names, as they have to be the same as the property names on data Why I kind of like it: It's very easy to set up and I don't have to think about it... Then again if I try to think, and change names to things that make sense, I shoot myself in the foot, and then I have to think about it! Option 3. Proposal: Inherit my view model from dependancy object, and notify binding sources of changes directly. Why I don't like it: I'm not even 100% sure dependancy properties/objects can DO this, it was just a thought to look into. Also I don't personally feel that WPF/SL types like Dep Obj belong at the view model level. Why I kind of like it: IF it has the capability that I'm seeking then it's a good answer! minus that pesky layering issue. Option 4. Proposal: Use a consistant agent messaging system based off of Task Parallels DataFlow Library to propogate everything through linked pipelining. Why I don't like it: I've never tried this, and somehow I think it will be lacking, plus it requires me to think about my code completely differently all the way around. Why I kind of like it: It has the possiblity of allowing me to do some VERY fun manipulations with a push based data model and using ActionBlocks as validation AND setters to then privately change view model properties and explicitly control PropertyChanged notifications.

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  • MVVM Binding Orthogonal Aspects in Views e.g. Application Settings

    - by chibacity
    I have an application which I am developing using WPF\Prism\MVVM. All is going well and I have some pleasing MVVM implementations. However, in some of my views I would like to be able to bind application settings e.g. when a user reloads an application, the checkbox for auto-scrolling a grid should be checked in the state it was last time the user used the application. My view needs to bind to something that holds the "auto-scroll" setting state. I could put this on the view-model, but applications settings are orthogonal to the purpose of the view-model. The "auto-scroll" setting is controlling an aspect of the view. This setting is just an example. There will be quite a number of them and splattering my view-models with properties to represent application settings (so I can bind them) feels decidedly yucky. One view-model per view seems to be de rigeuer... What is best\usual practice here? Splatter my view-models with application settings? Have multiple view-models per view so settings can be represented in their own right? Split views so that controls can bind to an ApplicationSettingsViewModel? = too many views? Something else? Edit 1 To add a little more context, I am developing a UI with a tabbed interface. Each tab will host a single widget and there a variety of widgets. Each widget is a Prism composition of individual views. Some views are common amongst widgets e.g. a file picker view. Whilst each widget is composed of several views, as a whole, conceptually a widget has a single set of user settings e.g. last file selected, auto-scroll enabled, etc. These need to be persisted and retrieved\applied when the application starts again, and the widget views are created. My question is focused on the fact that conceptually a widget has a single set of user settings which is at right-angles to the fact that a widget consists of many views. Each view in the widget has it's own view-model (which works nicely and logically) but if I stick to a one view-model per view, I would have to splatter each view-model with user settings appropriate to it. This doesn't sound right ?!?

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  • MVVM, Animations, Binding - I need a quick question answered.

    - by Peanut
    http://stackoverflow.com/questions/2455963/wpf-mvvm-dynamic-animation-using-storyboards There is a question i have found that relates directly to the issue I am having. The answer provided in that thread is a bit short, however. I did a little looking on google for 'attached properties' and i still remain a bit confused. Could someone shed a little light regarding this question? Perhaps provide a little sample code for the link stated above? Thanks in advance

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  • What types of objects should the ViewModel reference in the MVVM pattern?

    - by Blanthor
    I've seen quite a few examples of MVVM. I can see that the View should reference the ViewModel. I've seen recently an example of a ViewModel referencing a View, which seems wrong to me, as it would result in tighter coupling. Given that ViewModel is often described as an intermediary between the View and the Model, is there more to the ViewModel than a facade to domain objects? I hope I used the term "facade" correctly here.

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  • Messenger -"Register" an instance and not a type with the MVVM Light Toolkit?

    - by vidalsasoon
    Hello i'm consfused using the Messenger class of MVVM Light. I have a ProductsViewModel that can get initialized a number of times. In the constructor of ProductsViewModel I have this code: Messenger.Default.Register(this, n = MessageBox.Show(n.Test)); The problem is, if I have 2 instances of ProductsViewModel, then Messenger gets registered twice. Is is bad to Register the Messenger in a constructor? Hope this makes sense!

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  • Silverlight 4, MVVM and Test-Driven Development

    - by Martin Hinshelwood
    As part of his UK tour Microsoft's Jesse Liberty will be talking in Edinburgh for an evening on Silverlight 4. [Register Now, there are some places left]  The Talk MVVM and Silverlight to build test-driven programs Understanding Refactoring and Dependency Injection A Walk through of a non-trivial application The Speaker Jesse Liberty, Silverlight Geek, is a Developer Community Program Manager for Microsoft (US). Lately he has been focused on Component-based, Test-Driven, Cross-platform line-of-business application development, and has led the development of the open source  Silverlight HyperVideo Platform. Liberty is the author of over two dozen books, and his blog is a required resource for Silverlight programmers. His twenty years of programming experience include stints as a Distinguished Software Engineer at AT&T; Vice President of Human-Computer Interaction at Citibank and Software Architect at PBS/Learning Link. The Venue We are meeting at Microsoft's offices in Edinburgh in Waterloo Place. This is the building on the corner of North Bridge at the east end of Princes Street. Parking can be found at the nearby Greenside Row car park which is just off Leith Walk (used for the Omni Centre). The venue is approximately 2-3 minutes walk away from Edinburgh Waverly train station. The Agenda 18:30 Doors open 19:00 Welcome 19:10 Part 1 20:00 Break 20:10 Part 2 20:50 Feedback and Prizes 21:00 End   [Register Now, there are some places left] Technorati Tags: Silverlight,MVVM,TDD

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  • Handling DataGrid.SelectedItems in an MVVM-friendly manner

    - by Laurent Bugnion
    An interesting question from one of the MVVM Light users today: Is there an MVVM-friendly way to get a DataGrid’s SelectedItems into the ViewModel? The issue there is as old as the DataGrid (that’s not very old but still): SelectedItem (singular) is a DependencyProperty and can be databound to a property in the ViewModel. SelectedItems (plural) is not a DependencyProperty. Thankfully the answer is very simple: Use EventToCommand to call a Command in the ViewModel, and pass the SelectedItems collection as parameter. For example, if the command in the ViewModel is declared as follows:public RelayCommand<IList> SelectionChangedCommand { get; private set; }and (in the MainViewModel constructor):SelectionChangedCommand = new RelayCommand<IList>( items => { if (items == null) { NumberOfItemsSelected = 0; return; } NumberOfItemsSelected = items.Count; }); Then the XAML markup becomes:<sdk:DataGrid x:Name="MyDataGrid" ItemsSource="{Binding Items}"> <i:Interaction.Triggers> <i:EventTrigger EventName="SelectionChanged"> <cmd:EventToCommand Command="{Binding SelectionChangedCommand}" CommandParameter="{Binding SelectedItems, ElementName=MyDataGrid}" /> </i:EventTrigger> </i:Interaction.Triggers> </sdk:DataGrid> I slapped a quick sample and published it here (VS2010, SL4 but the concept works in SL3 and WPF too). Cheers! Laurent Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • MVVM Light V4.1 with support for Windows Phone 8

    - by Laurent Bugnion
    Today is a very exciting day: After the official release of Windows 8 (and Microsoft Surface!) on Friday, and the official release of Windows Phone 8 on Monday, the Build conference is starting! This is the conference in which we will learn all about the developer experience for Windows 8 and Windows Phone 8. As a partner of Microsoft, I had the privilege of trying out some of the new things early, and this gave me the opportunity to port MVVM Light to Windows Phone 8 (it was already running for Windows 8), and today I am officially publishing this new version. Before you go and update, please not the following: V4.1 (4.1.24.0) only supports Visual Studio 2012 (and Express). If for some reason you are still using Visual Studio 2010, don’t despair! In the next few days I will publish an update supporting these versions as well. But for now, please only upgrade if you are on VS12! That being said, here we go: The download page is available on Codeplex and you can download the updated MSI and install it. Please make sure to read the Readme HTML page that automatically opens in your web browser after the MSI completes! It contains important information on how to install selected Project and Item templates for the frameworks of your choice. This version also support the following versions of Visual Studio: Visual Studio 2012 Pro, Premium, Ultimate Visual Studio 2012 Express for Windows 8 Visual Studio 2012 Express for Windows Phone 8 Visual Studio 2012 Express for Web (Silverlight 4, Silverlight 5) Visual Studio 2012 Express for Windows Desktop (WPF3.5, WPF4, WPF4.5) We also support Expression Blend of course. Windows Phone 8 and Windows 8 are very very exciting opportunities for developers in the whole world. There are already a number of apps running on top of MVVM Light in the Windows Store and of course a large range of apps for Windows Phone too. With this release, we hope to support the developers and speed up application development. It is a pleasure to serve such an innovative and creative community! Happy coding Laurent   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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