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  • WP7: Why does a ListBox.ItemsPanel break my ElementName data binding?

    - by iguanaNet
    I have a Windows Phone 7 ListBox that binds to a list of integers. I am using the default MVVM Light template, so there is a ViewModel class that contains data and a simple RelayCommand. Here is the ListBox: <ListBox ItemsSource="{Binding MyData}"> <ListBox.ItemTemplate> <DataTemplate> <Button Content="{Binding}"> <i:Interaction.Triggers> <i:EventTrigger EventName="Click"> <cmd:EventToCommand Command="{Binding ElementName=ContentGrid, Path=DataContext.TestCommand}" CommandParameter="{Binding}" /> </i:EventTrigger> </i:Interaction.Triggers> </Button> </DataTemplate> </ListBox.ItemTemplate> </ListBox> This displays a vertical list of integers inside buttons. If you click any of them, the following command code executes and shows a pop-up: new RelayCommand<int>(i => MessageBox.Show("Test" + i)); However, if I simply add the following XAML to change to a horizontal list, the databinding fails. Nothing happens when you click the button and no error messages are written to the Output window. <ListBox.ItemsPanel> <ItemsPanelTemplate> <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" /> </ItemsPanelTemplate> </ListBox.ItemsPanel> I have tried some other types of binding for the EventToCommand. For example, specifying my ViewModel as a static resource. It works, but is less ideal than the example above. Why does that ItemsPanel break the databinding?

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  • Bind an Incode DataTemplate in WPF

    - by Mike Bynum
    I have a WPF Application which is using MVVM. I know that there ways of doing this in XAML but I am working on a plugin architecture and came up with a solution where a plugin exposes it's viewmodel to my plugin host's viewmodel and it's datatemplate. I want to leave the lifetime management of the plugin view up to WPF. I have tried having the plugins expose a UserControl but ran into issues when WPF decided to dispose of my UserControl so I would not reattach it without weird hacky work arounds. I am having issues getting some sort of binding working to where i can bind a control to the data and it's template to my data template. I have a ViewModel which looks something like: public class MyViewModel { public DataTemplate SelectedTemplate{ get; set;} public object SelectedViewModel {get; set;} } The selected template and viewmodel are determined somewhere else in the code but are irrelevant to my question. My question is how i can bind to a DataTemplate so that I know how to display the data shown in the SelectedViewModel. The DataTemplate is a DataTemplate created incode which respresents: <DataTemplate DataType="{x:Type vm:MyViewModel}"> <v:MyUserControl /> </DataTemplate> I have tried: <UserControl Template="{Binding Path=SelectedTemplate}" Content="{Binding Path=SelectedViewModel"} /> But UserControl expects a control template and not a data template.

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  • Choosing right control for list of items

    - by prostynick
    I am new to WPF and MVVM. In my ViewModel I have collection of items, for example: class Item { string Title {get; set;} string Description {get; set;} } I would like to create a view, so at the beginning I would have: Title1 Title2 Title3 If user click on one of title it will expand to show description, eg: Title1 Description1 Title2 Title3 If user click on other title, there will be two expanded items: Title1 Description1 Title2 Description2 Title3 This is probably very similar to Expander control and maybe I could use it, but I am doing it other way, to learn something new. What control should I use for this purpose? Should that be ItemsControl or maybe ListBox? I imagine, that if I use ItemsControl, I should probably extend my Item class to have something like bool IsExpanded and bind UI item visibility to that value. But maybe I could use ListBox and somehow bind UI item visibility to... Yeah, to what? :) How could I do such a simple thing?

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  • WPF Calling a custom command on a custom control (from a viewmodel?)

    - by user190615
    I want to take a snap of the visual tree of a custom wpf control when the user clicks a button in a toolbar. The control is bound to a viewmodel. I have a BitmapSource dp in the custom control holding the snapped image which is bound to a property on my VM. The BitmapSource dp on the control is updated via a custom command on the control. I've tied the toolbar button's command to call the controls command which updates the BitmapSource. Now the problem is the end result I want is when the user clicks the button, the control updates its image and then the vm offers to save this image. I cant wrap my mind around an mvvm way of doing this. One inelegant solution is that control fires an event after the image is updated which is routed to the viewmodel as a command(command behavior) but then if i want to do something else with the image on some other button click, all the commands bound to the events will fire. All thoughts appreciated. EDIT The command on the control is a RoutedCommand and the commands in my vm are Prism delegate commands.

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  • WPF: Setting DataContext of a UserControl with Binding not working in XAML

    - by Grant Crofton
    Hi, I'm trying to get my first WPF app working using MVVM, and I've hit a little binding problem. The setup is that I have a view & viewModel which holds User details (the parent), and to try and keep things simple I've put a section of that view into a separate view & viewModel (the child). The child view is defined as a UserControl. The issue I'm having is how to set the DataContext of the child view (the UserControl). My parent ViewModel has a property which exposes the child ViewModel, like so: class ParentViewModel: INotifyPropertyChanged { public ChildViewModel childViewModel { get; set; } //... } In the XAML for my parent view (which has it's DataContext set to the ParentViewModel), I try to set the DataContext of the child view as follows: <views:ChildView x:Name="ChildView" DataContext="{Binding childViewModel}"/> However, this doesn't work. The DataContext of the child view is set to the same DataContext as the parent view (i.e. the ParentViewModel), as if I wasn't setting it at all. I also tried setting the DataContext in the child view itself, which also doesn't work: <UserControl x:Class="DietRecorder.Client.View.ChildView" DataContext="childViewModel" I have found a couple of ways around this. In the child view, I can bind everything by including the ChildViewModel in the path: <SomeControl Visibility="{Binding Path=childViewModel.IsVisible}"> but I don't want the child view to have this level of awareness of the hierarchy. Setting the DataContext in code also works - however, I have to do this after showing the parent view, otherwise the DataContext just gets overwritten when I call Show(): parentView.Show(); parentView.ChildView.DataContext = parentViewModel.childViewModel; This code also makes me feel uneasy, what with the LOD violation and all. It's just the DataContext that seems to be the problem - I can bind other things in the child, for example I tried binding the FontSize to an int property just to test it: <views:ChildView x:Name="ChildView" FontSize="{Binding Path=someVal}"/> And that works fine. But I'm sure binding the DataContext should work - I've seen similar examples of this kind of thing. Have I missed something obvious here? Is there a reason this won't work? Is there a spelling mistake somewhere? (I renamed things for your benefit so you won't be able to help me there anyway). Any thoughts welcome. Thanks, Grant

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  • Defining InputBindings within a Style

    - by Brent
    I'm creating a WPF app using the MVVM design pattern, and I'm trying to extend the TabItem control so that it closes the tab when the user clicks the middle mouse button. I'm trying to achieve this using InputBindings, and it works very well until I try to define it within a style. I've learned that you cannot add InputBindings to a style unless you attach it using a DependencyProperty. So I followed this similar post here... and it works... almost. I can close one tab using the middle mouse button, but it won't work on any of the other tabs (all of the tabs are added at runtime and inherit the same style). So I need some help. Why would this only be working the first time, and not after? Obviously I could create a custom control that inherits from a TabItem and make it work, but I'd like to figure this out as I can see this being expanded in my projects. I'm no expert on DependencyProperties, so please help me out. Thanks! Style: <Style TargetType="{x:Type TabItem}"> <Setter Property="w:Attach.InputBindings"> <Setter.Value> <InputBindingCollection> <MouseBinding MouseAction="MiddleClick" Command="{Binding CloseCommand}"/> </InputBindingCollection> </Setter.Value> </Setter> ... </Style> Class public class Attach { public static readonly DependencyProperty InputBindingsProperty = DependencyProperty.RegisterAttached("InputBindings", typeof(InputBindingCollection), typeof(Attach), new FrameworkPropertyMetadata(new InputBindingCollection(), (sender, e) => { var element = sender as UIElement; if (element == null) return; element.InputBindings.Clear(); element.InputBindings.AddRange((InputBindingCollection)e.NewValue); })); public static InputBindingCollection GetInputBindings(UIElement element) { return (InputBindingCollection)element.GetValue(InputBindingsProperty); } public static void SetInputBindings(UIElement element, InputBindingCollection inputBindings) { element.SetValue(InputBindingsProperty, inputBindings); } }

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  • M-V-VM, isn't the Model leaking into the View?

    - by BFree
    The point of M-V-VM as we all know is about speraration of concerns. In patterns like MVVM, MVC or MVP, the main purpose is to decouple the View from the Data thereby building more flexible components. I'll demonstrate first a very common scenario found in many WPF apps, and then I'll make my point: Say we have some StockQuote application that streams a bunch of quotes and displays them on screen. Typically, you'd have this: StockQuote.cs : (Model) public class StockQuote { public string Symbol { get; set; } public double Price { get; set; } } StockQuoteViewModel.cs : (ViewModel) public class StockQuoteViewModel { private ObservableCollection<StockQuote> _quotes = new ObservableCollection<StockQuote>(); public ObservableCollection<StockQuote> Quotes { get { return _quotes; } } } StockQuoteView.xaml (View) <Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication1" Title="Window1" Height="300" Width="300"> <Window.DataContext> <local:StockQuoteViewModel/> </Window.DataContext> <Window.Resources> <DataTemplate x:Key="listBoxDateTemplate"> <StackPanel Orientation="Horizontal"> <TextBlock Text="{Binding Symbol}"/> <TextBlock Text="{Binding Price}"/> </StackPanel> </DataTemplate> </Window.Resources> <Grid> <ListBox ItemTemplate="{StaticResource listBoxDateTemplate}" ItemsSource="{Binding Quotes}"/> </Grid> </Window> And then you'd have some kind of service that would feed the ObservableCollection with new StockQuotes. My question is this: In this type of scenario, the StockQuote is considered the Model, and we're exposing that to the View through the ViewModel's ObservableCollection. Which basically means, our View has knowledge of the Model. Doesn't that violate the whole paradigm of M-V-VM? Or am I missing something here....?

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  • I know I'm doing something wrong with RaiseCanExecuteChanged and CanExecute

    - by Cowman
    Well after fiddling with MVVM light to get my button to enable and disable when I want it to... I sort of mashed things together until it worked. However, I just know I'm doing something wrong here. I have RaiseCanExecuteChanged and CanExecute in the same area being called. Surely this is not how it's done? Here's my xaml <Button Margin="10, 25, 10, 25" VerticalAlignment="Center" HorizontalAlignment="Center" Width="50" Height="50" Grid.Column="1" Grid.Row="3" Content="Host"> <i:Interaction.Triggers> <i:EventTrigger EventName="Click"> <mvvmLight:EventToCommand Command="{Binding HostChat}" MustToggleIsEnabled="True" /> </i:EventTrigger> </i:Interaction.Triggers> </Button> And here's my code public override void InitializeViewAndViewModel() { view = UnityContainer.Resolve<LoginPromptView>(); viewModel = UnityContainer.Resolve<LoginPromptViewModel>(); view.DataContext = viewModel; InjectViewIntoRegion(RegionNames.PopUpRegion, view, true); viewModel.HostChat = new DelegateCommand(ExecuteHostChat, CanHostChat); viewModel.PropertyChanged += new System.ComponentModel.PropertyChangedEventHandler(ViewModelPropertyChanged); } void ViewModelPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e) { if (e.PropertyName == "Name" || e.PropertyName == "Port" || e.PropertyName == "Address") { (viewModel.HostChat as DelegateCommand).RaiseCanExecuteChanged(); (viewModel.HostChat as DelegateCommand).CanExecute(); } } public void ExecuteHostChat() { } public bool CanHostChat() { if (String.IsNullOrEmpty(viewModel.Address) || String.IsNullOrEmpty(viewModel.Port) || String.IsNullOrEmpty(viewModel.Name)) { return false; } else return true; } See how these two are together? Surely that can't be right. I mean... it WORKS for me... but something seems wrong about it. Shouldn't RaiseCanExecuteChanged call CanExecute? It doesn't... and so if I don't have that CanExecute in there, my control never toggles its IsEnabled like I need it to. (viewModel.HostChat as DelegateCommand).RaiseCanExecuteChanged(); (viewModel.HostChat as DelegateCommand).CanExecute();

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  • Rendering a WPF Network Map/Graph layout - Manual? PathListBox? Something Else?

    - by Ben Von Handorf
    I'm writing code to present the user with a simplified network map. At any given time, the map is focused on a specific item... say a router or a server. Based on the focused item, other network entities are grouped into sets (i.e. subnets or domains) and then rendered around the focused item. Lines would represent connections and groups would be visually grouped inside a rectangle or ellipse. Panning and zooming are required features. An item can be selected to display more information in a "properties" style window. An item could also be double-clicked to re-focus the entire network map on that item. At that point, the entire map would be re-calculated. I am using MVVM without any framework, as of yet. Assume the logic for grouping items and determining what should be shown or not is all in place. I'm looking for the best way to approach the UI layout. So far, I'm aware of the following options: Use a canvas for layout (inside a ScrollViewer to handle the panning). Have my ViewModel make use of a Layout Manager type of class, which would handle assigning all the layout properties (Top, Left, etc.). Bind my set of display items to an ItemsControl and use Data Templates to handle the actual rendering. The drawbacks with this approach: Highly manual layout on my part. Lots of calculation. I have to handle item selection manually. Computation of connecting lines is manual. The Pros of this approach: I can draw additional lines between child subnets as appropriate (manually). Additional LayoutManagers could be added later to render the display differently. This could probably be wrapped up into some sort of a GraphLayout control to be re-used. Present the focused item at the center of the display and then use a PathListBox for layout of the additional items. Have my ViewModel expose a simple list of things to be drawn and bind them to the PathListBox. Override the ListBoxItem Template to also create a line geometry from the borders of the focused item (tricky) to the bound item. Use DataTemplates to handle the case where the item being bound is a subnet, in which case we would use another PathListBox in the template to display items inside the subnet. The drawbacks with this approach: Selected Item synchronization across multiple `PathListBox`es. Only one item on the whole graph can be selected at a time, but each child PathListBox maintains its own selection. Also, subnets cannot be selected, but would be selectable without additional work. Drawing the connecting lines is going to be a bit of trickery in the ListBoxItem template, since I need to know the correct side of the focused item to connect to. The pros of this approach: I get to stay out of the layout business, more. I'm looking for any advice or thoughts from others who have encountered similar issues or who have more WPF experience than I. I'm using WPF 4, so any new tricks are legal and encouraged.

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  • Using bindings to control column order in a DataGrid

    - by DanM
    Problem I have a WPF Toolkit DataGrid, and I'd like to be able to switch among several preset column orders. This is an MVVM project, so the column orders are stored in a ViewModel. The problem is, I can't get bindings to work for the DisplayIndex property. No matter what I try, including the sweet method in this Josh Smith tutorial, I get: The DisplayIndex for the DataGridColumn with Header 'ID' is out of range. DisplayIndex must be greater than or equal to 0 and less than Columns.Count. Parameter name: displayIndex. Actual value was -1. Is there any workaround for this? I'm including my test code below. Please let me know if you see any problems with it. ViewModel code public class MainViewModel { public List<Plan> Plans { get; set; } public int IdDisplayIndex { get; set; } public int NameDisplayIndex { get; set; } public int DescriptionDisplayIndex { get; set; } public MainViewModel() { Initialize(); } private void Initialize() { IdDisplayIndex = 1; NameDisplayIndex = 2; DescriptionDisplayIndex = 0; Plans = new List<Plan> { new Plan { Id = 1, Name = "Primary", Description = "Likely to work." }, new Plan { Id = 2, Name = "Plan B", Description = "Backup plan." }, new Plan { Id = 3, Name = "Plan C", Description = "Last resort." } }; } } Plan Class public class Plan { public int Id { get; set; } public string Name { get; set; } public string Description { get; set; } } Window code - this uses Josh Smith's DataContextSpy <Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication1" xmlns:mwc="http://schemas.microsoft.com/wpf/2008/toolkit" Title="Main Window" Height="300" Width="300"> <Grid> <mwc:DataGrid ItemsSource="{Binding Plans}" AutoGenerateColumns="False"> <mwc:DataGrid.Resources> <local:DataContextSpy x:Key="spy" /> </mwc:DataGrid.Resources> <mwc:DataGrid.Columns> <mwc:DataGridTextColumn Header="ID" Binding="{Binding Id}" DisplayIndex="{Binding Source={StaticResource spy}, Path=DataContext.IdDisplayIndex}" /> <mwc:DataGridTextColumn Header="Name" Binding="{Binding Name}" DisplayIndex="{Binding Source={StaticResource spy}, Path=DataContext.NameDisplayIndex}" /> <mwc:DataGridTextColumn Header="Description" Binding="{Binding Description}" DisplayIndex="{Binding Source={StaticResource spy}, Path=DataContext.DescriptionDisplayIndex}" /> </mwc:DataGrid.Columns> </mwc:DataGrid> </Grid> </Window> Note: If I just use plain numbers for DisplayIndex, everything works fine, so the problem is definitely with the bindings. Update 5/1/2010 I was just doing a little maintenance on my project, and I noticed that when I ran it, the problem I discuss in this post had returned. I knew that it worked last time I ran it, so I eventually narrowed the problem down to the fact that I had installed a newer version of the WPF Toolkit (Feb '10). When I reverted to the June '09 version, everything worked fine again. So, I'm now doing something I should have done in this first place: I'm including the WPFToolkit.dll that works in my solution folder and checking it into version control. It's unfortunate, though, that the newer toolkit has a breaking change.

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  • Databinding to ObservableCollection in a different UserControl - how to preserve current selections?

    - by Dave
    Scope of question expanded on 2010-03-25 I ended up figuring out my problem, but here's a new problem that came up as a result of solving the original question, because I want to be able to award the bounty to someone!!! Once I figured out my problem, I soon found out that when the ObservableCollection updates, the databound ComboBox has its contents repopulated, but most of the selections have been blanked out. I assume that in this case, MVVM is going to make it difficult for me to remember the last selected item. I have an idea, but it seems a little nasty. I'll award the bounty to whomever comes up with a nice solution for this! Question re-written on 2010-03-24 I have two UserControls, where one is a dialog that has a TabControl, and the other is one that appears within said TabControl. I'll just call them CandyDialog and CandyNameViewer for simplicity's sake. There's also a data management class called Tracker that manages information storage, which for all intents and purposes just exposes a public property that is an ObservableCollection. I display the CandyNameViewer in CandyDialog via code behind, like this: private void CandyDialog_Loaded( object sender, RoutedEventArgs e) { _candyviewer = new CandyViewer(); _candyviewer.DataContext = _tracker; candy_tab.Content = _candyviewer; } The CandyViewer's XAML looks like this (edited for kaxaml): <Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"> <Page.Resources> <DataTemplate x:Key="CandyItemTemplate"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="120"></ColumnDefinition> <ColumnDefinition Width="150"></ColumnDefinition> </Grid.ColumnDefinitions> <TextBox Grid.Column="0" Text="{Binding CandyName}" Margin="3"></TextBox> <!-- just binding to DataContext ends up using InventoryItem as parent, so we need to get to the UserControl --> <ComboBox Grid.Column="1" SelectedItem="{Binding SelectedCandy, Mode=TwoWay}" ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}, Path=DataContext.CandyNames}" Margin="3"></ComboBox> </Grid> </DataTemplate> </Page.Resources> <Grid> <ListBox DockPanel.Dock="Top" ItemsSource="{Binding CandyBoxContents, Mode=TwoWay}" ItemTemplate="{StaticResource CandyItemTemplate}" /> </Grid> </Page> Now everything works fine when the controls are loaded. As long as CandyNames is populated first, and then the consumer UserControl is displayed, all of the names are there. I obviously don't get any errors in the Output Window or anything like that. The issue I have is that when the ObservableCollection is modified from the model, those changes are not reflected in the consumer UserControl! I've never had this problem before; all of my previous uses of ObservableCollection updated fine, although in those cases I wasn't databinding across assemblies. Although I am currently only adding and removing candy names to/from the ObservableCollection, at a later date I will likely also allow renaming from the model side. Is there something I did wrong? Is there a good way to actually debug this? Reed Copsey indicates here that inter-UserControl databinding is possible. Unfortunately, my favorite Bea Stollnitz article on WPF databinding debugging doesn't suggest anything that I could use for this particular problem.

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  • How do I use constructor dependency injection to supply Models from a collection to their ViewModels

    - by GraemeF
    I'm using constructor dependency injection in my WPF application and I keep running into the following pattern, so would like to get other people's opinion on it and hear about alternative solutions. The goal is to wire up a hierarchy of ViewModels to a similar hierarchy of Models, so that the responsibility for presenting the information in each model lies with its own ViewModel implementation. (The pattern also crops up under other circumstances but MVVM should make for a good example.) Here's a simplified example. Given that I have a model that has a collection of further models: public interface IPerson { IEnumerable<IAddress> Addresses { get; } } public interface IAddress { } I would like to mirror this hierarchy in the ViewModels so that I can bind a ListBox (or whatever) to a collection in the Person ViewModel: public interface IPersonViewModel { ObservableCollection<IAddressViewModel> Addresses { get; } void Initialize(); } public interface IAddressViewModel { } The child ViewModel needs to present the information from the child Model, so it's injected via the constructor: public class AddressViewModel : IAddressViewModel { private readonly IAddress _address; public AddressViewModel(IAddress address) { _address = address; } } The question is, what is the best way to supply the child Model to the corresponding child ViewModel? The example is trivial, but in a typical real case the ViewModels have more dependencies - each of which has its own dependencies (and so on). I'm using Unity 1.2 (although I think the question is relevant across the other IoC containers), and I am using Caliburn's view strategies to automatically find and wire up the appropriate View to a ViewModel. Here is my current solution: The parent ViewModel needs to create a child ViewModel for each child Model, so it has a factory method added to its constructor which it uses during initialization: public class PersonViewModel : IPersonViewModel { private readonly Func<IAddress, IAddressViewModel> _addressViewModelFactory; private readonly IPerson _person; public PersonViewModel(IPerson person, Func<IAddress, IAddressViewModel> addressViewModelFactory) { _addressViewModelFactory = addressViewModelFactory; _person = person; Addresses = new ObservableCollection<IAddressViewModel>(); } public ObservableCollection<IAddressViewModel> Addresses { get; private set; } public void Initialize() { foreach (IAddress address in _person.Addresses) Addresses.Add(_addressViewModelFactory(address)); } } A factory method that satisfies the Func<IAddress, IAddressViewModel> interface is registered with the main UnityContainer. The factory method uses a child container to register the IAddress dependency that is required by the ViewModel and then resolves the child ViewModel: public class Factory { private readonly IUnityContainer _container; public Factory(IUnityContainer container) { _container = container; } public void RegisterStuff() { _container.RegisterInstance<Func<IAddress, IAddressViewModel>>(CreateAddressViewModel); } private IAddressViewModel CreateAddressViewModel(IAddress model) { IUnityContainer childContainer = _container.CreateChildContainer(); childContainer.RegisterInstance(model); return childContainer.Resolve<IAddressViewModel>(); } } Now, when the PersonViewModel is initialized, it loops through each Address in the Model and calls CreateAddressViewModel() (which was injected via the Func<IAddress, IAddressViewModel> argument). CreateAddressViewModel() creates a temporary child container and registers the IAddress model so that when it resolves the IAddressViewModel from the child container the AddressViewModel gets the correct instance injected via its constructor. This seems to be a good solution to me as the dependencies of the ViewModels are very clear and they are easily testable and unaware of the IoC container. On the other hand, performance is OK but not great as a lot of temporary child containers can be created. Also I end up with a lot of very similar factory methods. Is this the best way to inject the child Models into the child ViewModels with Unity? Is there a better (or faster) way to do it in other IoC containers, e.g. Autofac? How would this problem be tackled with MEF, given that it is not a traditional IoC container but is still used to compose objects?

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  • Game logic dynamically extendable architecture implementation patterns

    - by Vlad
    When coding games there are a lot of cases when you need to inject your logic into existing class dynamically and without making unnecessary dependencies. For an example I have a Rabbit which can be affected by freeze ability so it can't jump. It could be implemented like this: class Rabbit { public bool CanJump { get; set; } void Jump() { if (!CanJump) return; ... } } But If I have more than one ability that can prevent it from jumping? I can't just set one property because some circumstances can be activated simultanously. Another solution? class Rabbit { public bool Frozen { get; set; } public bool InWater { get; set; } bool CanJump { get { return !Frozen && !InWater; } } } Bad. The Rabbit class can't know all the circumstances it can run into. Who knows what else will game designer want to add: may be an ability that changes gravity on an area? May be make a stack of bool values for CanJump property? No, because abilities can be deactivated not in that order in which they were activated. I need a way to seperate ability logic that prevent the Rabbit from jumping from the Rabbit itself. One possible solution for this is making special checking event: class Rabbit { class CheckJumpEventArgs : EventArgs { public bool Veto { get; set; } } public event EventHandler<CheckJumpEvent> OnCheckJump; void Jump() { var args = new CheckJumpEventArgs(); if (OnCheckJump != null) OnCheckJump(this, args); if (!args.Veto) return; ... } } But it's a lot of code! A real Rabbit class would have a lot of properties like this (health and speed attributes, etc). I'm thinking of borrowing something from MVVM pattern where you have all the properties and methods of an object implemented in a way where they can be easily extended from outside. Then I want to use it like this: class FreezeAbility { void ActivateAbility() { _rabbit.CanJump.Push(ReturnFalse); } void DeactivateAbility() { _rabbit.CanJump.Remove(ReturnFalse); } // should be implemented as instance member // so it can be "unsubscribed" bool ReturnFalse(bool previousValue) { return false; } } Is this approach good? What also should I consider? What are other suitable options and patterns? Any ready to use solutions? UPDATE The question is not about how to add different behaviors to an object dynamically but how its (or its behavior) implementation can be extended with external logic. I don't need to add a different behavior but I need a way to modify an exitsing one and I also need a possibiliity to undo changes.

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  • View bound to paged collection view not updating all of the time.

    - by Thomas
    I new to silverlight and trying to make a business application using the mvvm pattern and ria services. I have a view model class that contains a PagedCollectoinView and it is set to the item source of a datagrid. When I update the PagedCollectionView the datagrid is only updated the first time then after that subsequent changes to the data to not reflect in the view until after another edit. Things seem to be delayed one edit. Below is a summarized example of my xaml and code behind. This is the code for my view model public class CustomerContactLinks : INotifyPropertyChanged { private ObservableCollection<CustomerContactLink> _CustomerContact; public ObservableCollection<CustomerContactLink> CustomerContact { get { if (_CustomerContact == null) _CustomerContact = new ObservableCollection<CustomerContactLink>(); return _CustomerContact; } set { _CustomerContact = value; } } private PagedCollectionView _CustomerContactPaged; public PagedCollectionView CustomerContactPaged { get { if (_CustomerContactPaged == null) _CustomerContactPaged = new PagedCollectionView(CustomerContact); return _CustomerContactPaged; } } private TicketSystemDataContext _ctx; public TicketSystemDataContext ctx { get { if (_ctx == null) _ctx = new TicketSystemDataContext(); return _ctx; } } public void GetAll() { ctx.Load(ctx.GetCustomerContactInfoQuery(), LoadCustomerContactsComplete, null); } private void LoadCustomerContactsComplete(LoadOperation<CustomerContactLink> lo) { foreach (var entity in lo.Entities) { CustomerContact.Add(entity as CustomerContactLink); } } #region INotifyPropertyChanged Members public event PropertyChangedEventHandler PropertyChanged; private void RaisePropertyChanged(string propertyName) { if (PropertyChanged != null) { this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } #endregion } Here is the basics of my XAML <Data:DataGrid x:Name="GridCustomers" MinHeight="100" MaxWidth="1000" IsReadOnly="True" AutoGenerateColumns="False"> <Data:DataGrid.Columns> <Data:DataGridTextColumn Header="First Name" Binding="{Binding Customer.FirstName}" Width="105" /> <Data:DataGridTextColumn Header="MI" Binding="{Binding Customer.MiddleName}" Width="35" /> <Data:DataGridTextColumn Header="Last Name" Binding="{Binding Customer.LastName}" Width="105"/> <Data:DataGridTextColumn Header="Address1" Binding="{Binding Contact.Address1}" Width="130"/> <Data:DataGridTextColumn Header="Address2" Binding="{Binding Contact.Address2}" Width="130"/> <Data:DataGridTextColumn Header="City" Binding="{Binding Contact.City}" Width="110"/> <Data:DataGridTextColumn Header="State" Binding="{Binding Contact.State}" Width="50"/> <Data:DataGridTextColumn Header="Zip" Binding="{Binding Contact.Zip}" Width="45"/> <Data:DataGridTextColumn Header="Home" Binding="{Binding Contact.PhoneHome}" Width="85"/> <Data:DataGridTextColumn Header="Cell" Binding="{Binding Contact.PhoneCell}" Width="85"/> <Data:DataGridTextColumn Header="Email" Binding="{Binding Contact.Email}" Width="118"/> </Data:DataGrid.Columns> </Data:DataGrid> <DataForm:DataForm x:Name="CustomerDetails" Header="Customer Details" AutoGenerateFields="False" AutoEdit="False" AutoCommit="False" CommandButtonsVisibility="Edit" Width="1000" Margin="0,5,0,0"> <DataForm:DataForm.EditTemplate> </DataForm:DataForm.EditTemplate> </DataForm:DataForm> And here is my code behind public Customers() { InitializeComponent(); BusyDialogIndicator.IsBusy = true; Loaded += new RoutedEventHandler(Customers_Loaded); CustomerDetails.BeginningEdit += new EventHandler(CustomerDetails_BeginningEdit); } void CustomerDetails_BeginningEdit(object sender, System.ComponentModel.CancelEventArgs e) { CustomerContacts.CustomerContactPaged.EditItem(CustomerDetails.CurrentItem); } private void Customers_Loaded(object sender, RoutedEventArgs e) { CustomerContacts = new CustomerContactLinks(); CustomerContacts.GetAll(); GridCustomers.ItemsSource = CustomerContacts.CustomerContactPaged; GridCustomerPager.Source = CustomerContacts.CustomerContactPaged; GridCustomers.SelectionChanged += new SelectionChangedEventHandler(GridCustomers_SelectionChanged); BusyDialogIndicator.IsBusy = false; } void GridCustomers_SelectionChanged(object sender, SelectionChangedEventArgs e) { CustomerDetails.CurrentItem = GridCustomers.SelectedItem as CustomerContactLink; } private void SaveChanges_Click(object sender, RoutedEventArgs e) { if (WebContext.Current.User.IsAuthenticated) { bool commited = CustomerDetails.CommitEdit(); if (commited && (!CustomerDetails.IsItemChanged && CustomerDetails.IsItemValid)) { CustomerContacts.Update(CustomerDetails.CurrentItem as CustomerContactLink); CustomerContacts.ctx.SubmitChanges(); CustomerContacts.CustomerContactPaged.CommitEdit(); CustomerContacts.CustomerContactPaged.Refresh(); (GridCustomers.ItemsSource as PagedCollectionView).Refresh(); } } }

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  • System.Timers.Timer leaking due to "direct delegate roots"

    - by alimbada
    Apologies for the rather verbose and long-winded post, but this problem's been perplexing me for a few weeks now so I'm posting as much information as I can in order to get this resolved quickly. We have a WPF UserControl which is being loaded by a 3rd party app. The 3rd party app is a presentation application which loads and unloads controls on a schedule defined by an XML file which is downloaded from a server. Our control, when it is loaded into the application makes a web request to a web service and uses the data from the response to display some information. We're using an MVVM architecture for the control. The entry point of the control is a method that is implementing an interface exposed by the main app and this is where the control's configuration is set up. This is also where I set the DataContext of our control to our MainViewModel. The MainViewModel has two other view models as properties and the main UserControl has two child controls. Depending on the data received from the web service, the main UserControl decides which child control to display, e.g. if there is a HTTP error or the data received is not valid, then display child control A, otherwise display child control B. As you'd expect, these two child controls bind two separate view models each of which is a property of MainViewModel. Now child control B (which is displayed when the data is valid) has a RefreshService property/field. RefreshService is an object that is responsible for updating the model in a number of ways and contains 4 System.Timers.Timers; a _modelRefreshTimer a _viewRefreshTimer a _pageSwitchTimer a _retryFeedRetrievalOnErrorTimer (this is only enabled when something goes wrong with retrieving data). I should mention at this point that there are two types of data; the first changes every minute, the second changes every few hours. The controls' configuration decides which type we are using/displaying. If data is of the first type then we update the model quite frequently (every 30 seconds) using the _modelRefreshTimer's events. If the data is of the second type then we update the model after a longer interval. However, the view still needs to be refreshed every 30 seconds as stale data needs to be removed from the view (hence the _viewRefreshTimer). The control also paginates the data so we can see more than we can fit on the display area. This works by breaking the data up into Lists and switching the CurrentPage (which is a List) property of the view model to the right List. This is done by handling the _pageSwitchTimer's Elapsed event. Now the problem My problem is that the control, when removed from the visual tree doesn't dispose of it's timers. This was first noticed when we started getting an unusually high number of requests on the web server end very soon after deploying this control and found that requests were being made at least once a second! We found that the timers were living on and not stopping hours after the control had been removed from view and that the more timers there were the more requests piled up at the web server. My first solution was to implement IDisposable for the RefreshService and do some clean up when the control's UnLoaded event was fired. Within the RefreshServices Dispose method I've set Enabled to false for all the timers, then used the Stop() method on all of them. I've then called Dispose() too and set them to null. None of this worked. After some reading around I found that event handlers may hold references to Timers and prevent them from being disposed and collected. After some more reading and researching I found that the best way around this was to use the Weak Event Pattern. Using this blog and this blog I've managed to work around the shortcomings in the Weak Event pattern. However, none of this solves the problem. Timers are still not being disabled or stopped (let alone disposed) and web requests are continuing to build up. Mem Profiler tells me that "This type has N instances that are directly rooted by a delegate. This can indicate the delegate has not been properly removed" (where N is the number of instances). As far as I can tell though, all listeners of the Elapsed event for the timers are being removed during the cleanup so I can't understand why the timers continue to run. Thanks for reading. Eagerly awaiting your suggestions/comments/solutions (if you got this far :-p)

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  • Silverlight data binding to parent user control's properties with using MVVM in both controls

    - by MagicMax
    Hello! I have two UserControls ("UserControlParentView" and "UserControlChildView") with MVVM pattern implemented in both controls. Parent control is a container for Child control and child control's property should be updated by data binding from Parent control in order to show/hide some check box inside Child control. Parent Control Description UserControlParentViewModel has property: private bool isShowCheckbox = false; public bool IsShowCheckbox { get { return isShowCheckbox; } set { isShowCheckbox = value; NotifyPropertyChanged("IsShowCheckbox"); } } UserControlParentViewModel - how I set DataContext of Parent control: public UserControlParentView() { InitializeComponent(); this.DataContext = new UserControlParentViewModel(); } UserControlParentView contains toggle button (in XAML), bound to UserControlParentViewModel's property IsShowCheckbox <ToggleButton Grid.Column="1" IsChecked="{Binding IsShowCheckbox, Mode=TwoWay}"></ToggleButton> Also Parent control contains instance of child element (somewhere in XAML) <local:UserControlChildView IsCheckBoxVisible="{Binding IsShowCheckbox}" ></local:UserControlChildView> so property in child control should be updated when user togggle/untoggle button. Child control contains Boolean property to be updated from parent control, but nothing happened! Breakpoint never fired! Property in UserControlChildView that should be updated from Parent control (here I plan to make chechBox visible/hidden in code behind): public bool IsCheckBoxVisible { get { return (bool)GetValue(IsCheckBoxVisibleProperty); } set { SetValue(IsCheckBoxVisibleProperty, value); } } // Using a DependencyProperty as the backing store for IsCheckBoxVisible. This enables animation, styling, binding, etc... public static readonly DependencyProperty IsCheckBoxVisibleProperty = DependencyProperty.Register("IsCheckBoxVisible", typeof(bool), typeof(TopMenuButton), new PropertyMetadata(false)); So the question is - what I'm doing wrong? Why child's property is never updated? BTW - there is no any binding error warnings in Output window...

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  • What should go in each MVVM triad?

    - by Harry
    OK, let's say I am creating a program that will list users contacts in a ListBox on the left side of the screen. When a user clicks on the contact, a bunch of messages or whatever appears in the main part of the window. Now my question is: how should the MVVM triads look? I have two models: Contact, and Message. The Contact model contains a list of Message models. Each ViewModel object will contain a single corresponding Model, right? And what about the Views? I have a "MainView" that is the main window, that will have things like the menu, toolbar etc. Do I put the ListBox in the MainView? My confusion is with what to put where; for example, what should the ContactView contain? Just a single instance of a contact? So the DataTemplate, ControlTemplate, context menus, styles etc for that single contact, and then just have a ListBox of them in the MainView...? Thanks.

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  • Sample code for my #mix10 talk online

    - by Laurent Bugnion
    I just saw that the video for my MIX10 session is online already! Impressive work, MIX10 team. I also published the sample code on my web server, so here are the links: Powerpoint slides Video MVVM Demo 1 (start) MVVM Demo 1 (final) Command sample RelayCommand sample Messaging sample MVVM Demo 2 (start) MVVM Demo 2 (final) MVVM Light Toolkit Version 3 It was a real pleasure and an amazing experience to have this talk and to get all the great feedback! Thanks all for coming, and as usual don’t hesitate to send your feedback! Laurent

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  • Visual Studio 2010 error: Type universe cannot resolve assembly

    - by dthrasher
    I've loaded a WPF project initially created in Visual Studio 2008 into Visual Studio 2010. The conversion process goes smoothly, but on certain XAML files the VS2010 designer throws several errors related to project references, including this one: System.Reflection.Adds.UnresolvedAssemblyException Type universe cannot resolve assembly: GalaSoft.MvvmLight, Version=3.0.0.31869, Culture=neutral, PublicKeyToken=3e875cdb3903c512. This assembly reference works just fine in the Expression Blend 4 designer, but not in VS2010. I can build and run the solution successfully. My solution targets the .Net Framework 3.5 SP1.

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  • MVVM- Trigger Storyboard in the View Model in Silverlight

    - by user275561
    I have a couple of Storyboards in my view that I would like to trigger from the ViewModel if possible. Is there a simple way or elegant way of doing this. Here is what I am trying to do. Person Clicks on a Button--RelayCommand (In the ViewModel), the Relay Command should then play the storyboard. Also one more thing, I would like to also trigger the storyboard animation by itself in the ViewModel without any interaction. <i:Interaction.Triggers> <i:EventTrigger EventName="MouseLeftButtonDown"> <cmd:EventToCommand Command="{Binding ButtonPress}" CommandParameterValue="RedButtonLight"> </cmd:EventToCommand> </i:EventTrigger> </i:Interaction.Triggers>

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  • Combobox with collection view itemssource does not update selection box item on changes to the Model

    - by Vinit Sankhe
    Hello, Sorry for the earlier lengthy post. Here is my concise (!) description. I bind a collection view to a combobox as a itemsSource and also bind its selectedvalue with a property from my view model. I must keep IsSynchronizedWithCurrentItem="False". I change the source list ofr the view and then refresh the view. The changed (added, removed, edited) items appear correctly in the item list of the combo. But problem is with the selected item. When I change its property which is also the displaymember path of the combo, the changed property value does not reflect back on the selecton box of the combo. If you open the combo dropdown it appears correctly on the item list but not on the selection box. Now if I change the combobox tag to Listbox in my XAML (keeping all attributes as it is) then when selected item's displaymember property value is updated, the changes reflect back on the selected item of the list box . Why this issue? Just FYI: My View Model has properties EmployeeCollectionView and SelectedEmployeeId which are bound to combo as ItemsSource and SelectedValue resp. This VM implements the INotifyPropertyChanged interface. My core employee class (list of which is the source for the EmployeeCollectionView) is simply a Model class without INotifyPropertyChanged. DisplayMemberPath is "Name" property of employee Model class. I change this by some means and expect the combo selection box to update the value. I tried refreshing ther SelectedEmployeeId by setting it 0 (where it correctly selects the dummy "-- Select All --" employee entry from itemsSource) and old selected value back. But no use. The old value takes me back to the old label. Items collection has latest entry though. When I make combobox's IsEditable=True before the view's refresh and after refresh I make IsEditable=False then the things work out correctly! But this is a patch and is unnecessary. Thx Vinit Sankhe

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  • problem with tabbed interface as mentioned in the article of josh smith

    - by Egi
    hello guys, i ve got a problem with my programm. here is the link: http://dl.dropbox.com/u/2734432/TabbedInterface.7z once u have opened both tabs, u ll start loosing the references to other collections of the current item in the view. that is because these ids are nullable and once you switch over to the other tab they ll become null. my question is why and how can i corrent that behavoir? if you change the int? to int there are no more problem, but i need them to be nullable!

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  • Databinding to ObservableCollection in a different UserControl?

    - by Dave
    Question re-written on 2010-03-24 I have two UserControls, where one is a dialog that has a TabControl, and the other is one that appears within said TabControl. I'll just call them CandyDialog and CandyNameViewer for simplicity's sake. There's also a data management class called Tracker that manages information storage, which for all intents and purposes just exposes a public property that is an ObservableCollection. I display the CandyNameViewer in CandyDialog via code behind, like this: private void CandyDialog_Loaded( object sender, RoutedEventArgs e) { _candyviewer = new CandyViewer(); _candyviewer.DataContext = _tracker; candy_tab.Content = _candyviewer; } The CandyViewer's XAML looks like this (edited for kaxaml): <Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"> <Page.Resources> <DataTemplate x:Key="CandyItemTemplate"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="120"></ColumnDefinition> <ColumnDefinition Width="150"></ColumnDefinition> </Grid.ColumnDefinitions> <TextBox Grid.Column="0" Text="{Binding CandyName}" Margin="3"></TextBox> <!-- just binding to DataContext ends up using InventoryItem as parent, so we need to get to the UserControl --> <ComboBox Grid.Column="1" SelectedItem="{Binding SelectedCandy, Mode=TwoWay}" ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}, Path=DataContext.CandyNames}" Margin="3"></ComboBox> </Grid> </DataTemplate> </Page.Resources> <Grid> <ListBox DockPanel.Dock="Top" ItemsSource="{Binding CandyBoxContents, Mode=TwoWay}" ItemTemplate="{StaticResource CandyItemTemplate}" /> </Grid> </Page> Now everything works fine when the controls are loaded. As long as CandyNames is populated first, and then the consumer UserControl is displayed, all of the names are there. I obviously don't get any errors in the Output Window or anything like that. The issue I have is that when the ObservableCollection is modified from the model, those changes are not reflected in the consumer UserControl! I've never had this problem before; all of my previous uses of ObservableCollection updated fine, although in those cases I wasn't databinding across assemblies. Although I am currently only adding and removing candy names to/from the ObservableCollection, at a later date I will likely also allow renaming from the model side. Is there something I did wrong? Is there a good way to actually debug this? Reed Copsey indicates here that inter-UserControl databinding is possible. Unfortunately, my favorite Bea Stollnitz article on WPF databinding debugging doesn't suggest anything that I could use for this particular problem.

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  • WPF ComboBox text inside ListBox

    - by geosteve
    I've got a list of ComboBoxes inside a listbox, like so: <ListBox ItemsSource="{Binding Values}"> <ListBox.ItemTemplate> <DataTemplate> <ComboBox ItemsSource="{...}" IsTextSearchEnabled="True" IsEditable="True"/> </DataTemplate> </ListBox.ItemTemplate> </ListBox> The Values for my listbox ItemsSouce is defined in my ViewModel as public ObservableCollection<string> Values { get; set; } How can I get the Text for each one of the ComboBoxes to show the Value for that particular ListBox item? (i.e. if values is {"a", "b", "c"} I want a list of 3 comboboxes showing "a", "b" and "c")

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