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  • View/ViewModel Interaction - Bindings, Commands and Triggers

    It looks like I have a set of posts on ViewModel, aka MVVM, that have organically emerged into a series or story of sorts. Recently, I blogged about The Case for ViewModel, and another on View/ViewModel Association using Convention and Configuration, and a long while back now, I posted an Introduction to the ViewModel Pattern as I was myself picking up this pattern, which has since become the natural way for me to program client applications. This installment adds to this on-going series. I've...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • ASP.NET MVC 2 - ViewModel Prefix

    - by Cosmo
    I want to use RenderPartial twice in my view with different models associated. The problem is that some properties are present in both models (nickname, password). They have no prefix, so even the id's or names are equal in the output. Now, if I have model errors for nickname or password, both fields get highlighted. Main View: <div> <% Html.RenderPartial("Register", Model.RegisterModel); %> </div> <div> <% Html.RenderPartial("Login", Model.LoginModel); %> </div> Login PartialView: <% using (Html.BeginForm("Login", "Member")) { %> <fieldset> <legend>Login</legend> <p> <%= Html.LabelFor(x => x.Nickname) %> <%= Html.TextBoxFor(x => x.Nickname) %> </p> <p> <%= Html.LabelFor(x => x.Password) %> <%= Html.PasswordFor(x => x.Password) %> </p> <input type="submit" value="Login" /> </fieldset> <% } % Register PartialView: <% using (Html.BeginForm("Register", "Member")) { %> <fieldset> <legend>Register</legend> <p> <%= Html.LabelFor(x => x.Nickname) %> <%= Html.TextBoxFor(x => x.Nickname) %> </p> <p> <%= Html.LabelFor(x => x.Email) %> <%= Html.TextBoxFor(x => x.Email) %> </p> <p> <%= Html.LabelFor(x => x.Password) %> <%= Html.PasswordFor(x => x.Password) %> </p> <p> <%= Html.LabelFor(x => x.PasswordRepeat) %> <%= Html.PasswordFor(x => x.PasswordRepeat) %> </p> <input type="submit" value="Register" /> </fieldset> <% } % How can I change this?

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  • ASP.NET MVC Viewmodel trouble...

    - by ile
    I've already started similar topic, but still didn't find final solution... So here I am with new one :) ... I'm developing NerdDinner from scratch and now I came to point where I define DinnerViewModel. Following these instructions (starting from Listing 5) I came to this: namespace Nerd.Controllers { // View Model Classes public class DinnerViewModel { public DinnerViewModel(List<Dinner> dinners) { this.Dinners = dinners; } public List<Dinner> Dinners { get; private set; } } public class DinnerController : Controller { private DinnerRepository dinnerRepository = new DinnerRepository(); .... public ActionResult NewDinners() { // Create list of products var dinners = new List<Dinner>(); dinners.Add(new Dinner(/*Something to add*/)); // Return view return View(new DinnerViewModel(dinners)); } } } Also, the Dinner table in this new version of NerdDinner is a bit shortened (it contains of DinnerID, Title, EventDate and Description fields). No matter what I try to add here dinners.Add(new Dinner(/*Something to add*/)); I always get following error Error 1 'Nerd.Model.Dinner' does not contain a constructor that takes '1' arguments C:\Documents and Settings\ilija\My Documents\Visual Studio 2008\Projects\Nerd\Nerd\Controllers\DinnerController.cs 150 25 Nerd Because I'm total beginner in C# and generally OOP, I have no idea what to do here... I suppose I need to declare a constructor, but how and where exactly? Thanks, Ile

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  • No Parameterless Constructor defined for - ViewModel with UOW

    - by TheVillageIdiot
    I have a view model class which uses UnitOfWork to some database operations like fetching of items to create select lists and IPrincipal for some auditing (like modified by etc.). It cannot work without this UOW. I have configured my web site to use Ninject to inject UOW into Controllers. From controller I pass this UOW when creating view model. But when performing POST operation I am getting No parameterless constructor defined for this object. I have few SelectList type of properties which I have excluded with Bind attribute. How can I overcome this problem? Can I configure Ninject to create the objects of this type and make ModelBinder use it?

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  • How do I implement a DataGrid with an MVVM approach.

    - by Fred
    Hi, I'd like to implement a sort of Addressbook/Contactbook using a Datagrid (or a List) and the MVVM pattern. Something like in Outlook/Thunderbird, where you've a list of your contacts displayed with a 2-3 main fields (name surname for example), and when you double-click a contact, then you get a new modal box that displays all the details of this specific contact. Since a couple of weeks/months, I'm reading a lot of stuff about MVVM pattern on the net, but somehow, I get confused. Until now, I could find any sample like this. (perhaps, I searched wrong?) How could I organize such an application? Thx in advance for your help.

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  • MVVM- Expose Model object in ViewModel

    - by Angel
    I have a wpf MVVM application , I exposed my model object into my viewModel by creating an instance of Model class (which cause dependency) into ViewModel , and instead of creating seperate VM properties , I wrap the Model properties inside my ViewModel Property. My model is just an entity framework generated proxy classes. Here is my Model class : public partial class TblProduct { public TblProduct() { this.TblPurchaseDetails = new HashSet<TblPurchaseDetail>(); this.TblPurchaseOrderDetails = new HashSet<TblPurchaseOrderDetail>(); this.TblSalesInvoiceDetails = new HashSet<TblSalesInvoiceDetail>(); this.TblSalesOrderDetails = new HashSet<TblSalesOrderDetail>(); } public int ProductId { get; set; } public string ProductCode { get; set; } public string ProductName { get; set; } public int CategoryId { get; set; } public string Color { get; set; } public Nullable<decimal> PurchaseRate { get; set; } public Nullable<decimal> SalesRate { get; set; } public string ImagePath { get; set; } public bool IsActive { get; set; } public virtual TblCompany TblCompany { get; set; } public virtual TblProductCategory TblProductCategory { get; set; } public virtual TblUser TblUser { get; set; } public virtual ICollection<TblPurchaseDetail> TblPurchaseDetails { get; set; } public virtual ICollection<TblPurchaseOrderDetail> TblPurchaseOrderDetails { get; set; } public virtual ICollection<TblSalesInvoiceDetail> TblSalesInvoiceDetails { get; set; } public virtual ICollection<TblSalesOrderDetail> TblSalesOrderDetails { get; set; } } Here is my ViewModel , public class ProductViewModel : WorkspaceViewModel { #region Constructor public ProductViewModel() { StartApp(); } #endregion //Constructor #region Properties private IProductDataService _dataService; public IProductDataService DataService { get { if (_dataService == null) { if (IsInDesignMode) { _dataService = new ProductDataServiceMock(); } else { _dataService = new ProductDataService(); } } return _dataService; } } //Get and set Model object private TblProduct _product; public TblProduct Product { get { return _product ?? (_product = new TblProduct()); } set { _product = value; } } #region Public Properties public int ProductId { get { return Product.ProductId; } set { if (Product.ProductId == value) { return; } Product.ProductId = value; RaisePropertyChanged("ProductId"); } } public string ProductName { get { return Product.ProductName; } set { if (Product.ProductName == value) { return; } Product.ProductName = value; RaisePropertyChanged(() => ProductName); } } private ObservableCollection<TblProduct> _productRecords; public ObservableCollection<TblProduct> ProductRecords { get { return _productRecords; } set { _productRecords = value; RaisePropertyChanged("ProductRecords"); } } //Selected Product private TblProduct _selectedProduct; public TblProduct SelectedProduct { get { return _selectedProduct; } set { _selectedProduct = value; if (_selectedProduct != null) { this.ProductId = _selectedProduct.ProductId; this.ProductCode = _selectedProduct.ProductCode; } RaisePropertyChanged("SelectedProduct"); } } #endregion //Public Properties #endregion // Properties #region Commands private ICommand _newCommand; public ICommand NewCommand { get { if (_newCommand == null) { _newCommand = new RelayCommand(() => ResetAll()); } return _newCommand; } } private ICommand _saveCommand; public ICommand SaveCommand { get { if (_saveCommand == null) { _saveCommand = new RelayCommand(() => Save()); } return _saveCommand; } } private ICommand _deleteCommand; public ICommand DeleteCommand { get { if (_deleteCommand == null) { _deleteCommand = new RelayCommand(() => Delete()); } return _deleteCommand; } } #endregion //Commands #region Methods private void StartApp() { LoadProductCollection(); } private void LoadProductCollection() { var q = DataService.GetAllProducts(); this.ProductRecords = new ObservableCollection<TblProduct>(q); } private void Save() { if (SelectedOperateMode == OperateModeEnum.OperateMode.New) { //Pass the Model object into Dataservice for save DataService.SaveProduct(this.Product); } else if (SelectedOperateMode == OperateModeEnum.OperateMode.Edit) { //Pass the Model object into Dataservice for Update DataService.UpdateProduct(this.Product); } ResetAll(); LoadProductCollection(); } #endregion //Methods } Here is my Service class: class ProductDataService:IProductDataService { /// <summary> /// Context object of Entity Framework model /// </summary> private MaizeEntities Context { get; set; } public ProductDataService() { Context = new MaizeEntities(); } public IEnumerable<TblProduct> GetAllProducts() { using(var context=new R_MaizeEntities()) { var q = from p in context.TblProducts where p.IsDel == false select p; return new ObservableCollection<TblProduct>(q); } } public void SaveProduct(TblProduct _product) { using(var context=new R_MaizeEntities()) { _product.LastModUserId = GlobalObjects.LoggedUserID; _product.LastModDttm = DateTime.Now; _product.CompanyId = GlobalObjects.CompanyID; context.TblProducts.Add(_product); context.SaveChanges(); } } public void UpdateProduct(TblProduct _product) { using (var context = new R_MaizeEntities()) { context.TblProducts.Attach(_product); context.Entry(_product).State = EntityState.Modified; _product.LastModUserId = GlobalObjects.LoggedUserID; _product.LastModDttm = DateTime.Now; _product.CompanyId = GlobalObjects.CompanyID; context.SaveChanges(); } } public void DeleteProduct(int _productId) { using (var context = new R_MaizeEntities()) { var product = (from c in context.TblProducts where c.ProductId == _productId select c).First(); product.LastModUserId = GlobalObjects.LoggedUserID; product.LastModDttm = DateTime.Now; product.IsDel = true; context.SaveChanges(); } } } I exposed my model object in my viewModel by creating an instance of it using new keyword, also I instantiated my DataService class in VM, I know this will cause a strong dependency. So , 1- Whats the best way to expose Model object in ViewModel ? 2- Whats the best way to use DataService in VM ?

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  • Connect ViewModel and View using Unity

    - by brainbox
    In this post i want to describe the approach of connecting View and ViewModel which I'm using in my last project.The main idea is to do it during resolve inside of unity container. It can be achived using InjectionFactory introduced in Unity 2.0 public static class MVVMUnityExtensions{    public static void RegisterView<TView, TViewModel>(this IUnityContainer container) where TView : FrameworkElement    {        container.RegisterView<TView, TView, TViewModel>();    }    public static void RegisterView<TViewFrom, TViewTo, TViewModel>(this IUnityContainer container)        where TViewTo : FrameworkElement, TViewFrom    {        container.RegisterType<TViewFrom>(new InjectionFactory(            c =>            {                var model = c.Resolve<TViewModel>();                var view = Activator.CreateInstance<TViewTo>();                view.DataContext = model;                return view;            }         ));    }}}And here is the sample how it could be used:var unityContainer = new UnityContainer();unityContainer.RegisterView<IFooView, FooView, FooViewModel>();IFooView view = unityContainer.Resolve<IFooView>(); // view with injected viewmodel in its datacontextPlease tell me your prefered way to connect viewmodel and view.

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  • Enum driving a Visual State change via the ViewModel

    - by Chris Skardon
    Exciting title eh? So, here’s the problem, I want to use my ViewModel to drive my Visual State, I’ve used the ‘DataStateBehavior’ before, but the trouble with it is that it only works for bool values, and the minute you jump to more than 2 Visual States, you’re kind of screwed. A quick search has shown up a couple of points of interest, first, the DataStateSwitchBehavior, which is part of the Expression Samples (on Codeplex), and also available via Pete Blois’ blog. The second interest is to use a DataTrigger with GoToStateAction (from the Silverlight forums). So, onwards… first let’s create a basic switch Visual State, so, a DataObj with one property: IsAce… public class DataObj : NotifyPropertyChanger { private bool _isAce; public bool IsAce { get { return _isAce; } set { _isAce = value; RaisePropertyChanged("IsAce"); } } } The ‘NotifyPropertyChanger’ is literally a base class with RaisePropertyChanged, implementing INotifyPropertyChanged. OK, so we then create a ViewModel: public class MainPageViewModel : NotifyPropertyChanger { private DataObj _dataObj; public MainPageViewModel() { DataObj = new DataObj {IsAce = true}; ChangeAcenessCommand = new RelayCommand(() => DataObj.IsAce = !DataObj.IsAce); } public ICommand ChangeAcenessCommand { get; private set; } public DataObj DataObj { get { return _dataObj; } set { _dataObj = value; RaisePropertyChanged("DataObj"); } } } Aaaand finally – hook it all up to the XAML, which is a very simple UI: A Rectangle, a TextBlock and a Button. The Button is hooked up to ChangeAcenessCommand, the TextBlock is bound to the ‘DataObj.IsAce’ property and the Rectangle has 2 visual states: IsAce and NotAce. To make the Rectangle change it’s visual state I’ve used a DataStateBehavior inside the Layout Root Grid: <i:Interaction.Behaviors> <ei:DataStateBehavior Binding="{Binding DataObj.IsAce}" Value="true" TrueState="IsAce" FalseState="NotAce"/> </i:Interaction.Behaviors> So now we have the button changing the ‘IsAce’ property and giving us the other visual state: Great! So – the next stage is to get that to work inside a DataTemplate… Which (thankfully) is easy money. All we do is add a ListBox to the View and an ObservableCollection to the ViewModel. Well – ok, a little bit more than that. Once we’ve got the ListBox with it’s ItemsSource property set, it’s time to add the DataTemplate itself. Again, this isn’t exactly taxing, and is purely going to be a Grid with a Textblock and a Rectangle (again, I’m nothing if not consistent). Though, to be a little jazzy I’ve swapped the rectangle to the other side (living the dream). So, all that’s left is to add some States to the template.. (Yes – you can do that), these can be the same names as the others, or indeed, something else, I have chosen to stick with the same names and take the extra confusion hit right on the nose. Once again, I add the DataStateBehavior to the root Grid element: <i:Interaction.Behaviors> <ei:DataStateBehavior Binding="{Binding IsAce}" Value="true" TrueState="IsAce" FalseState="NotAce"/> </i:Interaction.Behaviors> The key difference here is the ‘Binding’ attribute, where I’m now binding to the IsAce property directly, and boom! It’s all gravy!   So far, so good. We can use boolean values to change the visual states, and (crucially) it works in a DataTemplate, bingo! Now. Onwards to the Enum part of this (finally!). Obviously we can’t use the DataStateBehavior, it' only gives us true/false options. So, let’s give the GoToStateAction a go. Now, I warn you, things get a bit complex from here, instead of a bool with 2 values, I’m gonna max it out and bring in an Enum with 3 (count ‘em) 3 values: Red, Amber and Green (those of you with exceptionally sharp minds will be reminded of traffic lights). We’re gonna have a rectangle which also has 3 visual states – cunningly called ‘Red’, ‘Amber’ and ‘Green’. A new class called DataObj2: public class DataObj2 : NotifyPropertyChanger { private Status _statusValue; public DataObj2(Status status) { StatusValue = status; } public Status StatusValue { get { return _statusValue; } set { _statusValue = value; RaisePropertyChanged("StatusValue"); } } } Where ‘Status’ is my enum. Good times are here! Ok, so let’s get to the beefy stuff. So, we’ll start off in the same manner as the last time, we will have a single DataObj2 instance available to the Page and bind to that. Let’s add some Triggers (these are in the LayoutRoot again). <i:Interaction.Triggers> <ei:DataTrigger Binding="{Binding DataObject2.StatusValue}" Value="Amber"> <ei:GoToStateAction StateName="Amber" UseTransitions="False" /> </ei:DataTrigger> <ei:DataTrigger Binding="{Binding DataObject2.StatusValue}" Value="Green"> <ei:GoToStateAction StateName="Green" UseTransitions="False" /> </ei:DataTrigger> <ei:DataTrigger Binding="{Binding DataObject2.StatusValue}" Value="Red"> <ei:GoToStateAction StateName="Red" UseTransitions="False" /> </ei:DataTrigger> </i:Interaction.Triggers> So what we’re saying here is that when the DataObject2.StatusValue is equal to ‘Red’ then we’ll go to the ‘Red’ state. Same deal for Green and Amber (but you knew that already). Hook it all up and start teh project. Hmm. Just grey. Not what I wanted. Ok, let’s add a ‘ChangeStatusCommand’, hook that up to a button and give it a whirl: Right, so the DataTrigger isn’t picking up the data on load. On the plus side, changing the status is making the visual states change. So. We’ll cross the ‘Grey’ hurdle in a bit, what about doing the same in the DataTemplate? <Codey Codey/> Grey again, but if we press the button: (I should mention, pressing the button sets the StatusValue property on the DataObj2 being represented to the next colour). Right. Let’s look at this ‘Grey’ issue. First ‘fix’ (and I use the term ‘fix’ in a very loose way): The Dispatcher Fix This involves using the Dispatcher on the View to call something like ‘RefreshProperties’ on the ViewModel, which will in turn raise all the appropriate ‘PropertyChanged’ events on the data objects being represented. So, here goes, into turdcode-ville – population – me: First, add the ‘RefreshProperties’ method to the DataObj2: internal void RefreshProperties() { RaisePropertyChanged("StatusValue"); } (shudder) Now, add it to the hosting ViewModel: public void RefreshProperties() { DataObject2.RefreshProperties(); if (DataObjects != null && DataObjects.Count > 0) { foreach (DataObj2 dataObject in DataObjects) dataObject.RefreshProperties(); } } (double shudder) and now for the cream on the cake, adding the following line to the code behind of the View: Dispatcher.BeginInvoke(() => ((MoreVisualStatesViewModel)DataContext).RefreshProperties()); So, what does this *ahem* code give us: Awesome, it makes the single bound data object show the colour, but frankly ignores the DataTemplate items. This (by the way) is the same output you get from: Dispatcher.BeginInvoke(() => ((MoreVisualStatesViewModel)DataContext).ChangeStatusCommand.Execute(null)); So… Where does that leave me? What about adding a button to the Page to refresh the properties – maybe it’s a timer thing? Yes, that works. Right, what about using the Loaded event then eh? Loaded += (s, e) => ((MoreVisualStatesViewModel) DataContext).RefreshProperties(); Ahhh No. What about converting the DataTemplate into a UserControl? Anything is worth a shot.. Though – I still suspect I’m going to have to ‘RefreshProperties’ if I want the rectangles to update. Still. No. This DataTemplate DataTrigger binding is becoming a bit of a pain… I can’t add a ‘refresh’ button to the actual code base, it’s not exactly user friendly. I’m going to end this one now, and put some investigating into the use of the DataStateSwitchBehavior (all the ones I’ve found, well, all 2 of them are working in SL3, but not 4…)

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  • Serializing Complex ViewModel with Json.Net Destabilization Error on Latest Version

    - by dreadlocks1221
    I just added the latest Version of JSON.Net and I get the System.Security.VerificationException: Operation could destabilize the runtime error when trying to use a controller (while running the application). I read in other posts that this issue should have been fixed in release 6 but I still have the problem. I even added *Newtonsoft.* to the ignore modules in the intellitrace options, which seems to have suppressed the error, but the post will just run forever and not return anything. Any help I can get would be greatly appreciated. [HttpPost] public string GetComments(int ShowID, int Page) { int PageSize = 10; UserRepository UserRepo = new UserRepository(); ShowCommentViewModel viewModel = new ShowCommentViewModel(); IQueryable<Comment> CommentQuery = showRepository.GetShowComments(ShowID); var paginatedComments = new PaginatedList<Comment>(CommentQuery, Page, PageSize); viewModel.Comments = new List<CommentViewModel>(); foreach (Comment comment in CommentQuery.Take(10).ToList()) { CommentViewModel CommentModel = new CommentViewModel { Comment = comment, PostedBy = UserRepo.GetUserProfile(comment.UserID) }; IQueryable<Comment> ReplyQuery = showRepository.GetShowCommentReplies(comment.CommentID); int ReplyPage = 0; var paginatedReplies = new PaginatedList<Comment>(ReplyQuery, ReplyPage, 3); CommentModel.Replies = new List<ReplyModel>(); foreach (Comment reply in ReplyQuery.Take(3).ToList()) { ReplyModel rModel = new ReplyModel { Reply = reply, PostedBy = UserRepo.GetUserProfile(reply.UserID) }; CommentModel.Replies.Add(rModel); } CommentModel.RepliesNextPage = paginatedReplies.HasNextPage; CommentModel.RepliesPeviousPage = paginatedReplies.HasPreviousPage; CommentModel.RepliesTotalPages = paginatedReplies.TotalPages; CommentModel.RepliesPageIndex = paginatedReplies.PageIndex; CommentModel.RepliesTotalCount = paginatedReplies.TotalCount; viewModel.Comments.Add(CommentModel); } viewModel.CommentsNextPage = paginatedComments.HasNextPage; viewModel.CommentsPeviousPage = paginatedComments.HasPreviousPage; viewModel.CommentsTotalPages = paginatedComments.TotalPages; viewModel.CommentsPageIndex = paginatedComments.PageIndex; viewModel.CommentsTotalCount = paginatedComments.TotalCount; return JsonConvert.SerializeObject(viewModel, Formatting.Indented); }

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  • Adventures in MVVM &ndash; ViewModel Location and Creation

    - by Brian Genisio's House Of Bilz
    More Adventures in MVVM In this post, I am going to explore how I prefer to attach ViewModels to my Views.  I have published the code to my ViewModelSupport project on CodePlex in case you'd like to see how it works along with some examples.  Some History My approach to View-First ViewModel creation has evolved over time.  I have constructed ViewModels in code-behind.  I have instantiated ViewModels in the resources sectoin of the view. I have used Prism to resolve ViewModels via Dependency Injection. I have created attached properties that use Dependency Injection containers underneath.  Of all these approaches, I continue to find issues either in composability, blendability or maintainability.  Laurent Bugnion came up with a pretty good approach in MVVM Light Toolkit with his ViewModelLocator, but as John Papa points out, it has maintenance issues.  John paired up with Glen Block to make the ViewModelLocator more generic by using MEF to compose ViewModels.  It is a great approach, but I don’t like baking in specific resolution technologies into the ViewModelSupport project. I bring these people up, not to name drop, but to give them credit for the place I finally landed in my journey to resolve ViewModels.  I have come up with my own version of the ViewModelLocator that is both generic and container agnostic.  The solution is blendable, configurable and simple to use.  Use any resolution mechanism you want: MEF, Unity, Ninject, Activator.Create, Lookup Tables, new, whatever. How to use the locator 1. Create a class to contain your resolution configuration: public class YourViewModelResolver: IViewModelResolver { private YourFavoriteContainer container = new YourFavoriteContainer(); public YourViewModelResolver() { // Configure your container } public object Resolve(string viewModelName) { return container.Resolve(viewModelName); } } Examples of doing this are on CodePlex for MEF, Unity and Activator.CreateInstance. 2. Create your ViewModelLocator with your custom resolver in App.xaml: <VMS:ViewModelLocator x:Key="ViewModelLocator"> <VMS:ViewModelLocator.Resolver> <local:YourViewModelResolver /> </VMS:ViewModelLocator.Resolver> </VMS:ViewModelLocator> 3. Hook up your data context whenever you want a ViewModel (WPF): <Border DataContext="{Binding YourViewModelName, Source={StaticResource ViewModelLocator}}"> This example uses dynamic properties on the ViewModelLocator and passes the name to your resolver to figure out how to compose it. 4. What about Silverlight? Good question.  You can't bind to dynamic properties in Silverlight 4 (crossing my fingers for Silverlight 5), but you CAN use string indexing: <Border DataContext="{Binding [YourViewModelName], Source={StaticResource ViewModelLocator}}"> But, as John Papa points out in his article, there is a silly bug in Silverlight 4 (as of this writing) that will call into the indexer 6 times when it binds.  While this is little more than a nuisance when getting most properties, it can be much more of an issue when you are resolving ViewModels six times.  If this gets in your way, the solution (as pointed out by John), is to use an IndexConverter (instantiated in App.xaml and also included in the project): <Border DataContext="{Binding Source={StaticResource ViewModelLocator}, Converter={StaticResource IndexConverter}, ConverterParameter=YourViewModelName}"> It is a bit uglier than the WPF version (this method will also work in WPF if you prefer), but it is still not all that bad.  Conclusion This approach works really well (I suppose I am a bit biased).  It allows for composability from any mechanisim you choose.  It is blendable (consider serving up different objects in Design Mode if you wish... or different constructors… whatever makes sense to you).  It works in Cider.  It is configurable.  It is flexible.  It is the best way I have found to manage View-First ViewModel hookups.  Thanks to the guys mentioned in this article for getting me to something I love using.  Enjoy.

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  • WPF/MVVM - should we create a different Class for each ViewModel ?

    - by FMFF
    I'm attempting the example from the excellent "How Do I" video for MVVM by Todd Miranda found in MSDN. I'm trying to adapt the example for my learning purpose. In the example, he has a ViewModel called EmployeeListViewModel. Now if I want to include Departments, should I create another ViewModel such as DepartmentListViewModel? The example has EmployeeRepository as the Data Source. In my case, I'm trying to use an Entity object as the datasource (Employees.edmx in Model folder and EmployeeRepository.cs in DataAccess folder). If I want to display the list of Departments, should I create a separate class called DepartmentRepository and put all department related method definitions there? What if I want to retrieve the employee name and their department's name together? Where should I place the methods for this? I'm very new to WPF and MVVM and please let me know if any of the above needs to be re-phrased. Thank you for all the help.

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  • Rogue PropertyChanged notifications from ViewModel

    - by user1886323
    The following simple program is causing me a Databinding headache. I'm new to this which is why I suspect it has a simple answer. Basically, I have two text boxes bound to the same property myString. I have not set up the ViewModel (simply a class with one property, myString) to provide any notifications to the View for when myString is changed, so even although both text boxes operate a two way binding there should be no way that the text boxes update when myString is changed, am I right? Except... In most circumstances this is true - I use the 'change value' button at the bottom of the window to change the value of myString to whatever the user types into the adjacent text box, and the two text boxes at the top, even although they are bound to myString, do not change. Fine. However, if I edit the text in TextBox1, thus changing the value of myString (although only when the text box loses focus due to the default UpdateSourceTrigger property, see reference), TextBox2 should NOT update as it shouldn't receive any updates that myString has changed. However, as soon as TextBox1 loses focus (say click inside TextBox2) TextBox2 is updated with the new value of myString. My best guess so far is that because the TextBoxes are bound to the same property, something to do with TextBox1 updating myString gives TextBox2 a notification that it has changed. Very confusing as I haven't used INotifyPropertyChanged or anything like that. To clarify, I am not asking how to fix this. I know I could just change the binding mode to a oneway option. I am wondering if anyone can come up with an explanation for this strange behaviour? ViewModel: namespace WpfApplication1 { class ViewModel { public ViewModel() { _myString = "initial message"; } private string _myString; public string myString { get { return _myString; } set { if (_myString != value) { _myString = value; } } } } } View: <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" Title="MainWindow" Height="350" Width="525"> <Window.DataContext> <local:ViewModel /> </Window.DataContext> <Grid> <!-- The culprit text boxes --> <TextBox Height="23" HorizontalAlignment="Left" Margin="166,70,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" Text="{Binding Path=myString, Mode=TwoWay}" /> <TextBox Height="23" HorizontalAlignment="Left" Margin="166,120,0,0" Name="textBox2" VerticalAlignment="Top" Width="120" Text="{Binding Path=myString, Mode=TwoWay}"/> <!--The buttons allowing manual change of myString--> <Button Name="changevaluebutton" Content="change value" Click="ButtonUpdateArtist_Click" Margin="12,245,416,43" Width="75" /> <Button Content="Show value" Height="23" HorizontalAlignment="Left" Margin="12,216,0,0" Name="showvaluebutton" VerticalAlignment="Top" Width="75" Click="showvaluebutton_Click" /> <Label Content="" Height="23" HorizontalAlignment="Left" Margin="116,216,0,0" Name="showvaluebox" VerticalAlignment="Top" Width="128" /> <TextBox Height="23" HorizontalAlignment="Left" Margin="116,245,0,0" Name="changevaluebox" VerticalAlignment="Top" Width="128" /> <!--simply some text--> <Label Content="TexBox1" Height="23" HorizontalAlignment="Left" Margin="99,70,0,0" Name="label1" VerticalAlignment="Top" Width="61" /> <Label Content="TexBox2" Height="23" HorizontalAlignment="Left" Margin="99,118,0,0" Name="label2" VerticalAlignment="Top" Width="61" /> </Grid> </Window> Code behind for view: namespace WpfApplication1 { /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> public partial class MainWindow : Window { ViewModel viewModel; public MainWindow() { InitializeComponent(); viewModel = (ViewModel)this.DataContext; } private void showvaluebutton_Click(object sender, RoutedEventArgs e) { showvaluebox.Content = viewModel.myString; } private void ButtonUpdateArtist_Click(object sender, RoutedEventArgs e) { viewModel.myString = changevaluebox.Text; } } }

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  • How do I use DomainContext.Load in my ViewModel?

    - by kristian
    I'm trying to use RIA services to provide data to my Silverlight application by calling DomainContext.Load to retrieve a collection of widgets. I want to expose this collection through a property of the ViewModel so I can bind a control to the collection in my page. I think my approach must be fundamentally wrong because Load is called asynchronously and is therefore not available when my page loads and the control tried to bind. Can someone please show me the right way to do this? My Silverlight page has the following XAML: <navigation:Page x:Class="Demo.UI.Pages.WidgetPage" // the usual xmlns stuff here... xmlns:local="clr-namespace:Demo.UI.Pages" mc:Ignorable="d" xmlns:navigation="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Navigation" d:DataContext="{d:DesignInstance Type=local:WidgetPageModel, IsDesignTimeCreatable=False}" d:DesignWidth="640" d:DesignHeight="480" Title="Widget Page"> <Canvas x:Name="LayoutRoot"> <ListBox ItemsSource="{Binding RedWidgets}" Width="150" Height="500" /> </Canvas> </navigation:Page> My ViewModel looks like this: public class WidgetPageModel { private WidgetDomainContext WidgetContext { get; set; } public WidgetPageModel() { this.WidgetContext = new WidgetDomainContext(); WidgetContext.Load(WidgetContext.GetAllWidgetsQuery(), false); } public IEnumerable<Widget> RedWidgets { get { return this.WidgetContext.Widgets.Where(w => w.Colour == "Red"); } } }

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  • What is the appropriate granularity in building a ViewModel?

    - by JasCav
    I am working on a new project, and, after seeing some of the difficulties of previous projects that didn't provide enough separation of view from their models (specifically using MVC - the models and views began to bleed into each other a bit), I wanted to use MVVM. I understand the basic concept, and I'm excited to start using it. However, one thing that escapes me a bit - what data should be contained in the ViewModel? For example, if I am creating a ViewModel that will encompass two pieces of data so they can be edited in a form, do I capture it like this: public PersonAddressViewModel { public Person Person { get; set; } public Address Address { get; set; } } or like this: public PersonAddressViewModel { public string FirstName { get; set; } public string LastName { get; set; } public string StreetName { get; set; } // ...etc } To me, the first feels more correct for what we're attempting to do. If we were doing more fine grain forms (maybe all we were capturing was FirstName, LastName, and StreetAddress) then it might make more sense to go down to that level. But, I feel like the first is correct since we're capturing ALL Person data in the form and ALL Address data. It seems like it doesn't make sense (and a lot of extra work) to split things apart like that. Appreciate any insight.

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  • A really simple ViewModel base class with strongly-typed INotifyPropertyChanged

    - by Daniel Cazzulino
    I have already written about other alternative ways of implementing INotifyPropertyChanged, as well as augment your view models with a bit of automatic code generation for the same purpose. But for some co-workers, either one seemed a bit too much :o). So, back on the drawing board, we came up with the following view model authoring experience:public class MyViewModel : ViewModel, IExplicitInterface { private int value; public int Value { get { return value; } set { this.value = value; RaiseChanged(() =&gt; this.Value); } } double IExplicitInterface.DoubleValue { get { return value; } set { this.value = (int)value; RaiseChanged(() =&gt; ((IExplicitInterface)this).DoubleValue); } } } ...Read full article

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  • Passing ViewModel for backbone.js from MVC3 Server-Side

    - by Roman
    In ASP.NET MVC there is Model, View and Controller. MODEL represents entities which are stored in database and essentially is all the data used in a application (for example, generated by EntityFramework, "DB First" approach). Not all data from model you want to show in the view (for example, hashs of passwords). So you create VIEW MODEL, each for every strongly-typed-razor-view you have in application. Like this: using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace MyProject.ViewModels.SomeController.SomeAction { public class ViewModel { public ViewModel() { Entities1 = new List<ViewEntity1>(); Entities2 = new List<ViewEntity2>(); } public List<ViewEntity1> Entities1 { get; set; } public List<ViewEntity2> Entities2 { get; set; } } public class ViewEntity1 { //some properties from original DB-entity you want to show } public class ViewEntity2 { } } When you create complex client-side interfaces (I do), you use some pattern for javascript on client, MVC or MVVM (I know only these). So, with MVC on client you have another model (Backbone.Model for example), which is third model in application. It is a bit much. Why don`t we use the same ViewModel model on a client (in backbone.js or another framework)? Is there a way to transfer CS-coded model to JS-coded? Like in MVVM pattern, with knockout.js, when you can do like this: in SomeAction.cshtml: <div style="display: none;" id="view_model">@Json.Encode(Model)</div> after that in Javascript-code var ViewModel = ko.mapping.fromJSON($("#view_model").get(0).innerHTML); now you can extend your ViewModel with some actions, event handlers, etc: ko.utils.extend(ViewModel, { some_function: function () { //some code } }); So, we are not building the same view model on the client again, we are transferring existing view model from server. At least, data. But knockout.js is not suitable for me, you can`t build complex UI with it, it is just data-binding. I need something more structural, like backbone.js. The only way to build ViewModel for backbone.js I can see now is re-writing same ViewModel in JS from server with hands. Is there any ways to transfer it from server? To reuse the same viewmodel on server view and client view?

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  • How do I apply a ViewModel to the UserControl inside of a Page?

    - by Mike
    Doing something like this: <DataTemplate DataType="{x:Type vm:AllCustomersViewModel}"> <vw:AllCustomersView /> </DataTemplate> works in a ResourceDictionary for when I want to apply a ViewModel to a UserControl as root, but how do I the same thing when I have a UserControl inside of a Page? Would I create a ResourceDictionary for all my Pages then at the top of each Page do something like: <Page.Resources> <ResourceDictionary Source="../MainWindowResources.xaml"/> </Page.Resources> Any help is greatly appreciated, thanks!

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  • Including partial views when applying the Mode-View-ViewModel design pattern

    - by Filip Ekberg
    Consider that I have an application that just handles Messages and Users I want my Window to have a common Menu and an area where the current View is displayed. I can only work with either Messages or Users so I cannot work simultaniously with both Views. Therefore I have the following Controls MessageView.xaml UserView.xaml Just to make it a bit easier, both the Message Model and the User Model looks like this: Name Description Now, I have the following three ViewModels: MainWindowViewModel UsersViewModel MessagesViewModel The UsersViewModel and the MessagesViewModel both just fetch an ObserverableCollection<T> of its regarding Model which is bound in the corresponding View like this: <DataGrid ItemSource="{Binding ModelCollection}" /> The MainWindowViewModel hooks up two different Commands that have implemented ICommand that looks something like the following: public class ShowMessagesCommand : ICommand { private ViewModelBase ViewModel { get; set; } public ShowMessagesCommand (ViewModelBase viewModel) { ViewModel = viewModel; } public void Execute(object parameter) { var viewModel = new ProductsViewModel(); ViewModel.PartialViewModel = new MessageView { DataContext = viewModel }; } public bool CanExecute(object parameter) { return true; } public event EventHandler CanExecuteChanged; } And there is another one a like it that will show Users. Now this introduced ViewModelBase which only holds the following: public UIElement PartialViewModel { get { return (UIElement)GetValue(PartialViewModelProperty); } set { SetValue(PartialViewModelProperty, value); } } public static readonly DependencyProperty PartialViewModelProperty = DependencyProperty.Register("PartialViewModel", typeof(UIElement), typeof(ViewModelBase), new UIPropertyMetadata(null)); This dependency property is used in the MainWindow.xaml to display the User Control dynamicly like this: <UserControl Content="{Binding PartialViewModel}" /> There are also two buttons on this Window that fires the Commands: ShowMessagesCommand ShowUsersCommand And when these are fired, the UserControl changes because PartialViewModel is a dependency property. I want to know if this is bad practice? Should I not inject the User Control like this? Is there another "better" alternative that corresponds better with the design pattern? Or is this a nice way of including partial views?

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  • What the best way to wire up Entity Framework database context (model) to ViewModel in MVVM WPF?

    - by hal9k2
    As in the question above: What the best way to wire up Entity Framework database model (context) to viewModel in MVVM (WPF)? I am learning MVVM pattern in WPF, alot of examples shows how to implement model to viewModel, but models in that examples are just simple classes, I want to use MVVM together with entity framework model (base first approach). Whats the best way to wire model to viewModel. Thanks for answers. //ctor of ViewModel public ViewModel() { db = new PackageShipmentDBEntities(); // Entity Framework generated class ListaZBazy = new ObservableCollection<Pack>(db.Packs.Where(w => w.IsSent == false)); } This is my usual ctor of ViewModel, think there is a better way, I was reading about repository pattern, not sure if I can adapt this to WPF MVVM

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  • WPF USer Control viewmodel binding

    - by Senthilkumar
    HI Can any one suggest me how bind viewmodel to a usercontrol.. Also please share different way of doing that.. I have added viewmodel and view into my xaml file in namespace and in the user control resource tag.. i have defined a data template with data type as the viewmodel wh i have wrote.. inside that i have added my view (i mean the same usercontrol ih which im editing now is it possible -- please let me know).. I have used content control with content={Binding}.. and contenttemplate as a datatemplate.. in that i have reffered the property which i want to bind from viewmodel).. but its not binding as such.. My query is different ways of binding viewmodel to view in UserControlLibrary Project ?

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  • Why does this ActionFilterAttribute not import data to the ViewModel?

    - by Tomas Lycken
    I have the following attribute public class ImportStatusAttribute : ActionFilterAttribute { public override void OnActionExecuted(ActionExecutedContext filterContext) { var model = (IHasStatus)filterContext.Controller.ViewData.Model; model.Status = (StatusMessageViewModel)filterContext.Controller.TempData["status"]; filterContext.Controller.ViewData.Model = model; } } which I test with the following test method (the first of several I'll write when this one passes...) [TestMethod] public void OnActionExecuted_ImportsStatusFromTempDataToModel() { // Arrange Expect(new { Status = new StatusMessageViewModel() { Subject = "The test", Predicate = "has been tested" }, Key = "status" }); var filterContext = new Mock<ActionExecutedContext>(); var model = new Mock<IHasStatus>(); var tempData = new TempDataDictionary(); var viewData = new ViewDataDictionary(model.Object); var controller = new FakeController() { ViewData = viewData, TempData = tempData }; tempData.Add(expected.Key, expected.Status); filterContext.Setup(c => c.Controller).Returns(controller); var attribute = new ImportStatusAttribute(); // Act attribute.OnActionExecuted(filterContext.Object); // Assert Assert.IsNotNull(model.Object.Status, "The status was not exported"); Assert.AreEqual(model.Object.Status.ToString(), ((StatusMessageViewModel)expected.Status).ToString(), "The status was not the expected"); } (Expect() is a method that saves some expectations in the expected object...) When I run the test, it fails on the first assertion, and I can't get my head around why. Debugging, I can see that model is populated correctly, and that (StatusMessageViewModel)filterContext.Controller.TempData["status"] has the correct data. But after model.Status = (StatusMessageViewModel)filterContext.Controller.TempData["status"]; model.Status is still null in my watch window. Why can't I do this?

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