![]() ![]() If an existing model implementation encapsulates existing business logic, it can be difficult or risky to change it.The benefits of using the MVVM pattern are as follows: Therefore, the view model isolates the view from the model, and allows the model to evolve independently of the view. At a high level, the view "knows about" the view model, and the view model "knows about" the model, but the model is unaware of the view model, and the view model is unaware of the view. In addition to understanding the responsibilities of each component, it's also important to understand how they interact. The diagram below shows the relationships between the three components. There are three core components in the MVVM pattern: the model, the view, and the view model. It can also significantly improve code re-use opportunities and allows developers and UI designers to collaborate more easily when developing their respective parts of an app. Maintaining a clean separation between application logic and the UI helps address numerous development issues and makes an application easier to test, maintain, and evolve. The MVVM pattern helps cleanly separate an application's business and presentation logic from its user interface (UI). These issues include the tight coupling between the UI controls and the business logic, which increases the cost of making UI modifications, and the difficulty of unit testing such code. Complex maintenance issues can arise as apps are modified and grow in size and scope. NET MAUI developer experience typically involves creating a user interface in XAML, and then adding code-behind that operates on the user interface. Once the implementation is complete, it'll be available for download here.The. How to use an XDocument along with Lambda expression and Linq for the sample application is updated in my blog site.Hopefully my article will help someone to think in terms of view models. Special thanks to Josh for the Treeview article which made a paradigm shift to my thought process. Thinking in terms of ViewModels doesn't come by itself. Still thinking what it is that I'm missing here to make it non focussable. Points of Interestįunny thing to be noticed here is that the Separator is a focussable item even if we have set the Focussable property to false. Output shows you the hierarchy of menu items being loaded and also the Separator items. Public MenuSampleWindow(MenuItemViewModel menuItemViewModel) This viewmodel has a direct mapping to the Player business object and inherits MenuItemViewModel class. We can also have properties like IconSource in the menuitemviewmodel which will have a direct mapping to the Source Property of an Icon which can be used in a MenuItem. It has a Header property which is bound with the Header property of MenuItem, i.e., the presentation property. The menuitemviewmodel is also associated with a parent view model in case a parent exists. The menuitemviewmodel has a virtual method LoadChildMenuItems which will be overridden and used to load child menuitems in the application. public MenuItemViewModel ParentViewModel / /// Gets or sets the parent view model. _header = value NotifyOnPropert圜hanged( " Header") public ObservableCollection ChildMenuItems Private ObservableCollection _childMenuItems ![]() _childMenuItems = new ObservableCollection() Public MenuItemViewModel(MenuItemViewModel parentViewModel) / /// Initializes a new instance of the /// class. Public class MenuItemViewModel : BaseViewModel The Propert圜hanged event notifies the UI about the changes happening to the property in the View Model. Let’s have a look at the Project structure that I have maintained:Ī BaseViewModel class is maintained which has the implementation for INotifyPropert圜hanged interface which enables to have the Propert圜hanged. ![]() Header of the Menu Item is bound to the mapping property in the View Model which is mapped to let's same a Name property in the model. So what a View Model object generally encloses is the state of the model and the properties associated with the presentation layer like IsEnabled, Icon etc. Realizing a Menu Item as a View Model makes the implementation far easier and also enables separation of concern. What I have tried to achieve is to reuse the implementation of Treeview that Josh had done on WPF menus. If you have not gone through the article, please have a look as it is a must read for all MVVM aspirants. It opened at least my eyes and made me realize that a monster like a Treeview in WPF can be easily overwhelmed using a ViewModel approach. This article is inspired from the works of Josh Smith, mainly his implementation of the TreeView. This article is an attempt to visualize a WPF menu using the MVVM architecture. ![]()
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