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• WPF Drag and Drop - Get original source info from DragEventArgs

  - by Quinn351

  I am trying write Drag and Drop functionality using MVVM which will allow me to drag PersonModel objects from one ListView to another. This is almost working but I need to be able to get the ItemsSource of the source ListView from the DragEventArgs which I cant figure out how to do. private void OnHandleDrop(DragEventArgs e) { if (e.Data != null && e.Data.GetDataPresent("myFormat")) { var person = e.Data.GetData("myFormat") as PersonModel; //Gets the ItemsSource of the source ListView .. //Gets the ItemsSource of the target ListView and Adds the person to it ((ObservableCollection<PersonModel>)(((ListView)e.Source).ItemsSource)).Add(person); } } Any help would be greatly appreciated. Thanks!

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• Validation.HasError attached property

  - by Nima

  Did I miss something? 1- Style <Style TargetType="{x:Type TextBox}"> <Style.Triggers> <DataTrigger Binding="{Binding Path=Validation.HasError}" Value="true"> <Setter Property="BorderBrush" Value="Blue" /> </DataTrigger> </Style.Triggers> <Setter Property="MinWidth" Value="160" /> <Setter Property="Margin" Value="0 7 0 0"/> </Style> 2 - Viewmodel implement IDataErrorInfo 3- textBox in view <TextBox x:Name="FirstName" Text="{Binding Person.FirstName, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=true}"></TextBox> 3 - I use Caliburn MVVM I got " BindingExpression path error: 'Validation' property not found on 'object' ''PersonWindowViewModel' (HashCode=38783181)'. BindingExpression:Path=Validation.HasError; DataItem='PersonWindowViewModel' (HashCode=38783181); target element is 'TextBox' (Name='FirstName'); target property is 'NoTarget' (type 'Object')"S

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• Why state cannot be part of Presenter in MVP?

  - by rFactor

  I read http://www.codeproject.com/KB/architecture/MVC_MVP_MVVM_design.aspx and it said: As powerful as they are, both MVC and MVP have their problems. One of them is persistence of the View’s state. For instance, if the Model, being a domain object, does not know anything about the UI, and the View does not implement any business logic, then where would we store the state of the View’s elements such as selected items? Fowler comes up with a solution in the form of a Presentation Model pattern. I wonder why Presenter can't hold View state? It already holds all View logic. As far as I understand, in MVC and MVP the state is kept in View. In PM and MVVM the state is kept in the Presentation Model. Why can't Presenter follow PM in this particular case and contain the state of the view? Here is another article which says Presenter does not hold View state, instead the view does: http://www.codeproject.com/KB/aspnet/ArchitectureComparison.aspx

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• ICOmmand - canexecute can not disable Button with image content.

  - by Anish

  Hi , I have a button control in my wpf-mvvm application. I use an ICommand property (defined in viewmodel) to bind the button click event to viewmodel. I have - execute and canexecute parameters for my ICommand implementation (RelayCommand). Even if CanExecute is false...button is not disabled...WHEN button CONTENT is IMAGE But, when button content is text..enable/disable works fine. <Button DockPanel.Dock="Top" Command="{Binding Path=MoveUpCommand}"> <Button.Content> <Image Source="/Resources/MoveUpArrow.png"></Image> </Button.Content> <Style> <Style.Triggers> <Trigger Property="IsEnabled" Value="False"> <Setter Property="Opacity" Value=".5" /> </Trigger> </Style.Triggers> </Style> </Button>

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• CommandManager "cannot resolve symbol"

  - by Budda

  After adding "RelayCommand" class (that uses CommandManager class) into my Silverlight App I've got an error: The name 'CommandManager' does not exist in the current context This class is a member of System.Windows.Input namespace that is in PresentationCore.dll assembly. The problem is that I can't add this dll into my app... I am having a strange assumption: this class (CommmandManager) can't be used in the Silverlight. Am I right? How can I implement MVVM-pattern (http://msdn.microsoft.com/en-us/magazine/dd419663.aspx)? Thanks.

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• Set ListBoxItem.IsSelected when child TextBox is Focused

  - by jpsstavares

  Hi, I have a typical MVVM scenario: I have a ListBox that is binded to a List of StepsViewModels. I define a DataTemplate so that StepViewModels are rendered as StepViews. The StepView UserControl have a set of labels and TextBoxs. What I want to do is to select the ListBoxItem that is wrapping the StepView when a textBox is focused. I've tried to create a style for my TextBoxs with the following trigger: <Trigger Property="IsFocused" Value="true"> <Setter TargetName="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBoxItem}}}" Property="IsSelected" Value="True"/> </Trigger> But I get an error telling me that TextBoxs don't have an IsSelected property. I now that but the Target is a ListBoxItem. How can I make it work?

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• Cannot seem to communicate between views

  - by devnet247

  Hi all I have written a MVVM prototype as a learning exercise and I am struggling to understand how I can communicate between views.Let me explain I have a treeview on the left (leftSideView) ListView on the right (rightSideView) MainWindow (includes the 2 views mentioned above and a splitter) What I have implemented does not work and I would like you if you can point out where I am going wrong or if there is a better way of doing it. you can download the quick prototype from here http://cid-9db5ae91a2948485.skydrive.live.com/self.aspx/.Public/WpfCommunicationBetweenViews.zip For sure I am doing something wrong with the bindind. Also it would be nice to learn how you do it. EG ListBox on left (one view) ListView On the right (another view) how u communicate between the two. Thanks a lot of any suggestions

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• Is it considered bad practice to have ViewModel objects hold the Dispatcher?

  - by stiank81

  My WPF application is structured using the MVVM pattern. The ViewModels will communicate asynchronously with a server, and when the requested data is returned a callback in the ViewModel is triggered, and it will do something with this data. This will run on a thread which is not the UI Thread. Sometimes these callbacks involve work that needs to be done on the UI thread, so I need the Dispatcher. This might be things such as: Adding data to an ObservableCollection Trigger Prism commands that will set something to be displayed in the GUI Creating WPF objects of some kind. I try to avoid the latter, but the two first points here I find to be reasonable things for ViewModels to do. So; is it okay to have ViewModels hold the Dispatcher to be able to Invoke commands for the UI thread? Or is this considered bad practice? And why?

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• Best way to attach row from datagrid to EF.

  - by AKoran

  Using MVVM and EF...I have a datagrid binding to a View Model (using ObservableCollection). The view model has a save command which simply calls the SaveChanges command of the Data Context. However, when a user adds a new row to the datagrid, the new entity is detached. Is there any easy way to automatically attach it when it gets created. Currently, I'm having to do this in the Save command of my View Model and it seems a bit clunky: foreach (var dataItem in _DataList) // where _DataList is the ObservableCollection { if (dataItem.EntityState == EntityState.Detached) { _DataContext.AddToTestTables(dataItem); } } _DataContext.SaveChanges();

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• Activate WPF command based on TextBox value

  - by zendar

  This is MVVM application. I have form and related view model class. There is TextBox, Button and ListBox on form. Button is bound to DelegateCommand that has CanExecute function. Idea is that user enters some data in text box, presses button and data is appended to list box. I would like to enable command (and button) when user enters correct data in TextBox. Things look like this now: CanExecute() contains code that checks if data in property bound to text box is correct. Text box is bound to property in view model UpdateSourceTrigger is set to PropertyChanged and property in view model is updated after each key user presses. Problem is that CanExecute() does not fire when user enters data in text box. It doesn't fire even when text box lose focus. How could I make this work?

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• WPF Prism deactivate ?

  - by 2Fast4YouBR

  Hi all, I have an problem and would like to know if it is common problem or jsut with me. I am using Wpf with Prism and Unity, all with the pattern MvvM. I am loading a viewModel that has a reference to a dropdown with few items, my idea is that each time that the user click in some place to open the view that has this dropdown is that the dropdown will be shown with diferent values. The problem is that I see is that after I show the view for the first time and after the first DEACTIVATE, when I try to load it again looks like it is already in the memory (was not deactivated/disposed), so as is already in memory, it not call the constructor again of the modelView and the dropdown is shown with tha same old values. public BranchSelectionViewModel(IUnityContainer unityContainer) { this.unityContainer = unityContainer; User user = this.unityContainer.Resolve<User>(); this.branches = new ObservableCollection<Department>(user.Departments .Where(department => department.DepartmentId != user.SelectedDepartment.DepartmentId)); }

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• Why doesn't my viewmodel properties get populated

  - by Jakob

  Hi. I've looked all over and I can't figure out why my viewmodel doesn't get populated. I have this code: Followers = new ObservableCollection<aspnet_User>(_followersRepo.aspnet_Users); _followersRepo.Load(_followersRepo.GetUsersFollowingIDQuery(CurrentUserId)); Following = new ObservableCollection<aspnet_User>(_followingRepo.aspnet_Users); _followingRepo.Load(_followingRepo.GetUsersFollowedByIDQuery(CurrentUserId)); CurrentUser = _fullUserRepo.FullUsers.SingleOrDefault(); _fullUserRepo.Load(_fullUserRepo.GetFullUserByIDQuery(CurrentUserId)); But when I debug, there is no data loaded to the Followers, Following and CurrentUser objects. I know that data should be returned because I'm trying to implement the MVVM pattern in my app, and haven't changed the domainservice. Also I can se debugging the CurrentUserId has a value.

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• Disable Adding Item to Collection

  - by Wonko the Sane

  Hi All, I'm sure there's an "easy" answer to this, but for the moment it escapes me. In an MVVM application, I have a property that is a ObservableCollection, used for displaying some set of elements on the view. private readonly ObservableCollection<MyType> mMyCollection = new ObservableCollection<MyType>(); public ObservableCollection<MyType> MyCollection { get { return mMyCollection; } } I want to restrict consumers of this collection from simply using the property to add to the collection (i.e. I want to prevent this from the view): viewModel.MyCollection.Add(newThing); // want to prevent this! Instead, I want to force the use of a method to add items, because there may be another thread using that collection, and I don't want to modify the collection while that thread is processing it. public void AddToMyCollection(MyType newItem) { // Do some thread/task stuff here } Thanks, wTs

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• Light Peak, "le successeur de l'USB 3", devrait débarquer dès la fin de l'année avec des taux de tra

  Pour Intel, l'USB 3 a déjà un successeur : Light Peak Qui pourra atteindre les 10 Gbps et qui devrait débarquer dès fin 2010 Il y a à peine une an, Intel dévoilait Light Peak, une technologie de transfert de données par fibre optique qui flirte avec les 10 Gbps... soit le double de l'USB 3. Or l'USB 3 semble tarder à s'imposer. Les propos de Kevin Kahn, senior manager chez Intel lors de l'Intel Developer Forum de Pékin, n'en ont que plus de résonance. "Nous voyons [Light Peak] comme le successeur logique de l'USB 3.0. D'une certaine manière nous aimerions réaliser le tout dernier cable dont vous aurez besoin". Même si une période de cohabitation des deux ...

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• Validation of WPF User Input using MVVM and Entity Framework 4.0

  - by Emad

  I am building a WPF 4.0 Application using MVVM. The Model is generated using Entity Framework 4.0. I am using Data binding on the WPF to bind the user input to model properties. What is the easiest way to validate user input ? I prefer an approach where I can set the validation rules on the Model rather than on the WPF itself. How can this be done? Any samples are appreciated.

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• Passing a parameter using RelayCommand defined in the ViewModel (from Josh Smith example)

  - by eesh

  I would like to pass a parameter defined in the XAML (View) of my application to the ViewModel class by using the RelayCommand. I followed Josh Smith's excellent article on MVVM and have implemented the following. XAML Code <Button Command="{Binding Path=ACommandWithAParameter}" CommandParameter="Orange" HorizontalAlignment="Left" Style="{DynamicResource SimpleButton}" VerticalAlignment="Top" Content="Button"/> ViewModel Code public RelayCommand _aCommandWithAParameter; /// <summary> /// Returns a command with a parameter /// </summary> public RelayCommand ACommandWithAParameter { get { if (_aCommandWithAParameter == null) { _aCommandWithAParameter = new RelayCommand( param => this.CommandWithAParameter("Apple") ); } return _aCommandWithAParameter; } } public void CommandWithAParameter(String aParameter) { String theParameter = aParameter; } #endregion I set a breakpoint in the CommandWithAParameter method and observed that aParameter was set to "Apple", and not "Orange". This seems obvious as the method CommandWithAParameter is being called with the literal String "Apple". However, looking up the execution stack, I can see that "Orange", the CommandParameter I set in the XAML is the parameter value for RelayCommand implemenation of the ICommand Execute interface method. That is the value of parameter in the method below of the execution stack is "Orange", public void Execute(object parameter) { _execute(parameter); } What I am trying to figure out is how to create the RelayCommand ACommandWithAParameter property such that it can call the CommandWithAParameter method with the CommandParameter "Orange" defined in the XAML. Is there a way to do this? Why do I want to do this? Part of "On The Fly Localization" In my particular implementation I want to create a SetLanguage RelayCommand that can be bound to multiple buttons. I would like to pass the two character language identifier ("en", "es", "ja", etc) as the CommandParameter and have that be defined for each "set language" button defined in the XAML. I want to avoid having to create a SetLanguageToXXX command for each language supporting and hard coding the two character language identifier into each RelayCommand in the ViewModel.

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• MVC2 DataAnnotations on ViewModel - ModelState.isValid Always Returns true

  - by ScottSEA

  I have an MVC2 Application that uses MVVM pattern. I am trying use Data Annotations to validate form input. In my ThingsController I have two methods: [HttpGet] public ActionResult Index() { return View(); } public ActionResult Details(ThingsViewModel tvm) { if (!ModelState.IsValid) return View(tvm); try { Query q = new Query(tvm.Query); ThingRepository repository = new ThingRepository(q); tvm.Airplanes = repository.All(); return View(tvm); } catch (Exception) { return View(); } } My Details.aspx view is strongly typed to the ThingsViewModel: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<Config.Web.Models.ThingsViewModel>" %> The ViewModel is a class consisting of a IList of returned Thing objects and the Query string (which is submitted on the form) and has the Required data annotation: public class ThingsViewModel { public IList<Thing> Things{ get; set; } [Required(ErrorMessage="You must enter a query")] public string Query { get; set; } } When I run this, and click the submit button on the form without entering a value I get a YSOD with the following error: The model item passed into the dictionary is of type 'Config.Web.Models.ThingsViewModel', but this dictionary requires a model item of type System.Collections.Generic.IEnumerable`1[Config.Domain.Entities.Thing]'. How can I get Data Annotations to work with a ViewModel? I cannot see what I'm missing or where I'm going wrong - the VM was working just fine before I started mucking around with validation.

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• How create a Firefox-like search textbox in WPF?

  - by Simon

  Hey there. I'm writing an application in WPF using the MVVM-pattern and will really often use TextBoxes. I don't want to use labels for the user to know user what the text box is for, i.e. I don't want something like this: <TextBlock> Name: </TextBlock> <TextBox /> Instead, I would like the TextBox to contain its own label. Statically, you would express it like this: <TextBox>Name</TextBox> If the cursor is displayed in the textbox, i.e. the TextBox gains focus, I want the description text to disappear. If the TextBox is left empty and it loses the focus, the description text should be shown again. It's similar to the search textbox of StackOverflow or the one of Firefox. (please tell me if your not sure what I mean). One TextBox's label may change at runtime, dependending on e.g. a ComboBox's selected element or a value in my ViewModel. (It's like in Firefox's search TextBox, if you select google from the search engins' menu, the TextBox's label changes to "Google", if you select "Yahoo" its set to "Yahoo"). Thus I want to be able to bind the label's content. Consider that I may already have a Binding on the Text-Property of the TextBox. How can implement such a behaviour and make it reusable for any of my TextBox's? Code is welcome but not needed; a description of what to do is enough. Thank you in advance.

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• How to achieve "Blendability" when using DataServiceCollection in my ViewModel

  - by andlju

  I'm looking at using oData endpoints in my Silverlight client. Naturally, I'm doing MVVM and I want the project to be nice and "Blendable" (i.e. I must be able to cleanly use static data instead of the oData endpoints when in design mode.) Now to the problem. I'd like to use the DataServiceCollection in my ViewModels, since it allows for nice bindable collections without having to worry too much with BeginExecute/EndExecute etc. Now, let's look at some code. My Model interface looks like this: public interface ITasksModel { IQueryable<Task> Tasks { get; } } The oData endpoint implementation of that interface: public class TasksModel : ITasksModel { Uri svcUri = new Uri("http://localhost:2404/Services/TasksDataService.svc"); TaskModelContainer _container; public TasksModel() { _container = new TaskModelContainer(svcUri); } public IQueryable<Task> Tasks { get { return _container.TaskSet; } } } And the "Blendable" design-time implementation: public class DesignModeTasksModel : ITasksModel { private List<Task> _taskCollection = new List<Task>(); public DesignModeTasksModel() { _taskCollection.Add(new Task() { Id = 1, Title = "Task 1" }); _taskCollection.Add(new Task() { Id = 2, Title = "Task 2" }); _taskCollection.Add(new Task() { Id = 3, Title = "Task 3" }); } public IQueryable<Task> Tasks { get { return _taskCollection.AsQueryable(); } } } However, when I try to use this last one in my ViewModel constructor: public TaskListViewModel(ITasksModel tasksModel) { _tasksModel = tasksModel; _tasks = new DataServiceCollection<Task>(); _tasks.LoadAsync(_tasksModel.Tasks); } I get an exception: Only a typed DataServiceQuery object can be supplied when calling the LoadAsync method on DataServiceCollection. First of all, if this is the case, why not make the input parameter of LoadAsync be typed as DataServiceQuery? Second, what is the "proper" way of doing what I'm trying to accomplish?

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• LINQ to Entities exceptions (ElementAtOrDefault and CompareObjectEqual)

  - by OffApps Cory

  I am working on a shipping platform which will eventually automate shipping through several major carriers. I have a ShipmentsView Usercontrol which displayes a list of Shipments (returned by EntityFramework), and when a user clicks on a shipment item, it spawns a ShipmentEditView and passes the ShipmentID (RecordKey) to that view. I initially wrestled with trying to get the context from the parent (ShipmentsView) and finally gave up resolving to get to it later. I wanted to do this to keep a single instance of the context. anyhow, I now create a new instance of the context in my ShipmentEditViewModel, and query against it for the Shipment record. I know I could just pass the record, but I wanted to use the Ocean Framework that Karl Shifflett wrote and don't want to muck about writing new transition methods. So anyhow, I query and when stepping through, I can see that it returns a record, as soon as execution reached the point where it assigned the query result to the e.Result property, it throws up the following exception depending on the query I used. LINQToEntities Dim RecordID As Decimal = CDec(e.Argument) Dim myResult = From ship In _Context.Shipment _ Where ship.ShipID = e.Argument _ Select ship Select Case myResult.Count Case 0 e.Result = New Shipment Case 1 e.Result = myResult(0) Case Else e.Result = Nothing End Select "LINQ to Entities does not recognize the method 'System.Object.CompareObjectEqual(System.Object, System.Object, Boolean)' method, and this method cannot be translated into a store expression. LINQToEntities via Method calls Dim RecordID As Decimal = CDec(e.Argument) Dim myResult = _Context.Shipment.Where(Function(s) s.ShipID = RecordID) Select Case myResult.Count Case 0 e.Result = New Shipment Case 1 e.Result = myResult(0) Case Else e.Result = Nothing End Select LINQ to Entities does not recognize the method 'SnazzyShippingDAL.Shipment ElementAtOrDefault[Shipment] (System.Linq.IQueryable`1[SnazzyShippingDAL.Shipment], Int32)' method, and this method cannot be translated into a store expression. I have been trying to get this thing to display a record for like three days. i am seriously thinking about going back and re=-engineering it without the MVVM pattern (which I realize I am only starting to learn and understand) if only to make the &$^%ed thing work. Any help will be muchly appreciated. Cory

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• how to create and track multiple pairs "View-ViewModel"?

  - by Gianluca Colucci

  Hi! I am building an application that is based on MVVM-Light. I am in the need of creating multiple instances of the same View, and each one should bind to its own ViewModel. The default ViewModelLocator implements ViewModels as singletons, therefore different instances of the same View will bind to the same ViewModel. I could create the ViewModel in the VMLocator as a non-static object (as simple as returning new VM()...), but that would only partially help me. In fact, I still need to keep track of the opened windows. Nevertheless, each window might open several other windows (of a different kind, though). In this situation I might need to execute some operation on the parent View and all its children. For example before closing the View P, I might want to close all its children (view C1, view C2, etc.). Hence, is there any simple and easy way to achieve this? Or is there any best practice you would advice me to follow? Thanks in advance for your precious help. Cheers, Gianluca.

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• Binding to WPF ViewModel properties

  - by MartinHN

  I'm just playing around with WPF and MVVM, and I have made a simple app that displays a Rectangle that changes color whenever Network availability changes. But when that happens, I get this error: Cannot use a DependencyObject that belongs to a different thread than its parent Freezable. Code XAML <Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Window1" Height="400" Width="600"> <DockPanel LastChildFill="True"> <Rectangle x:Name="networkStatusRectangle" Width="200" Height="200" Fill="{Binding NetworkStatusColor}" /> </DockPanel> </Window> Code-behind using System.Windows; using WpfApplication1.ViewModels; namespace WpfApplication1 { /// <summary> /// Interaction logic for Window1.xaml /// </summary> public partial class Window1 : Window { public Window1() { InitializeComponent(); DataContext = new NetworkViewModel(); } } } ViewModel using System.ComponentModel; using System.Net.NetworkInformation; using System.Windows.Media; namespace WpfApplication1.ViewModels { public class NetworkViewModel : INotifyPropertyChanged { private Brush _NetworkStatusColor; public Brush NetworkStatusColor { get { return _NetworkStatusColor; } set { _NetworkStatusColor = value; NotifyOfPropertyChange("NetworkStatusColor"); } } public NetworkViewModel() { NetworkChange.NetworkAvailabilityChanged += new NetworkAvailabilityChangedEventHandler(NetworkChange_NetworkAvailabilityChanged); } protected void NetworkChange_NetworkAvailabilityChanged(object sender, NetworkAvailabilityEventArgs e) { if (e.IsAvailable) { this.NetworkStatusColor = new SolidColorBrush(Colors.Green); } else { this.NetworkStatusColor = new SolidColorBrush(Colors.Red); } } public event PropertyChangedEventHandler PropertyChanged = delegate { }; public void NotifyOfPropertyChange(string propertyName) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } } I assume that I should change the NetworkStatusColor property by invoking something?

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• RelayCommand sender from ItemsControl item

  - by Padu Merloti

  I've been using MVVM's RelayCommand with success to bind actions to XAML, but I'm having a small problem with my ItemsControl. <ItemsControl ItemsSource="{Binding Devices}" > <ItemsControl.ItemTemplate> <DataTemplate> <Grid Width="100" Margin="4" > <Button Command="{Binding Path=SelectDeviceCommand}" > <Grid> <Image Source="img_small.png"></Image> <Image Source="{Binding Path=Logo}" /> </Grid> </Button> </Grid> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl> In my view model: public RelayCommand SelectDeviceCommand { get; set; } private ObservableCollection<Device> Devices; Devices = CreateListOfDevices(); private void InitializeCommands() { SelectDeviceCommand = new RelayCommand((s) => MessageBox.Show(s.ToString())); } How do I define my SelectDeviceCommand in my view model in order to receive object that is bound to that item? My SelectDeviceCommand is not even being called... (but that I guess is because I need to make my Device a mini-viewmodel and implement the SelectDeviceCommand in it, is that correct?)

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• Get the value for a WPF binding

  - by Jose

  Ok, I didn't want a bunch of ICommands in my MVVM ViewModels so I decided to create a MarkupExtension for WPF that you feed it a string(the name of the method), and it gives you back an ICommand that executes the method. here's a snippet: public class MethodCall : MarkupExtension { public MethodCall(string methodName) { MethodName = methodName; CanExecute = "Can" + methodName; } public override object ProvideValue(IServiceProvider serviceProvider) { Binding bin= new Binding { Converter = new MethodConverter(MethodName,CanExecute) }; return bin.ProvideValue(serviceProvider); } } public class MethodConverter : IValueConverter { string MethodName; public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { //Convert to ICommand ICommand cmd = ConvertToICommand(); if (cmd == null) Debug.WriteLine(string.Format("Could not bind to method 'MyMethod' on object",MethodName)); return cmd; } } It works great, except when the binding fails(e.g. you mistype). When you do this in xaml: {Binding MyPropertyName} you see in the output window whenever the binding fails. and it tells you the propertyName the Type name etc. The MethodConverter Class can tell you the name of the method that failed, but it can't tell you the source object type. Because the value will be null. I can't figure out how to store the source object type so for the following class public class MyClass { public void MyMethod() { } } and the following xaml: <Button Command={d:MethodCall MyMethod}>My Method</Button> It currently says: "Could not bind to method 'MyMethod' on object but I would like it to say: "Could not bind to method 'MyMethod' on object MyClass Any ideas?

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• ViewModel updates after Model server roundtrip

  - by Pavel Savara

  I have stateless services and anemic domain objects on server side. Model between server and client is POCO DTO. The client should become MVVM. The model could be graph of about 100 instances of 20 different classes. The client editor contains diverse tab-pages all of them live-connected to model/viewmodel. My problem is how to propagate changes after server round-trip nice way. It's quite easy to propagate changes from ViewModel to DTO. For way back it would be possible to throw away old DTO and replace it whole with new one, but it will cause lot of redrawing for lists/DataTemplates. I could gather the server side changes and transmit them to client side. But the names of fields changed would be domain/DTO specific, not ViewModel specific. And the mapping seems nontrivial to me. If I should do it imperative way after round-trip, it would break SOC/modularity of viewModels. I'm thinking about some kind of mapping rule engine, something like automappper or emit mapper. But it solves just very plain use-cases. I don't see how it would map/propagate/convert adding items to list or removal. How to identify instances in collections so it could merge values to existing instances. As well it should propagate validation/error info. Maybe I should implement INotifyPropertyChanged on DTO and try to replay server side events on it ? And then bind ViewModel to it ? Would binding solve the problems with collection merges nice way ? Is EventAgregator from PRISM useful for that ? Is there any event record-replay component ? Is there better client side pattern for architecture with server side logic ?

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