However, views can also be represented by a data template, which specifies the UI elements to be used to visually represent an object when it's displayed. NET MAUI application, a view is typically a ContentPage-derived or ContentView-derived class. However, in some cases, the code-behind might contain UI logic that implements visual behavior that is difficult to express in XAML, such as animations. Ideally, each view is defined in XAML, with a limited code-behind that does not contain business logic. The view is responsible for defining the structure, layout, and appearance of what the user sees on screen. The following sections discuss the responsibilities of each of the classes in the MVVM pattern. The key to using MVVM effectively lies in understanding how to factor app code into the correct classes and how the classes interact. Designers can focus on the view, while developers can work on the view model and model components.
![wpf mvvm treeview example wpf mvvm treeview example](https://docs.devexpress.com/WPF/images/treeview-control.png)
Designers and developers can work independently and concurrently on their components during development.Therefore, a new version of the view should work with the existing view model. The app UI can be redesigned without touching the view model and model code, provided that the view is implemented entirely in XAML or C#.The unit tests for the view model can exercise exactly the same functionality as used by the view. Developers can create unit tests for the view model and the model, without using the view.In this scenario, the view model acts as an adapter for the model classes and prevents you from making major changes to the model code. 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.
![wpf mvvm treeview example wpf mvvm treeview example](https://img2020.cnblogs.com/blog/1648026/202111/1648026-20211127135206933-767097787.png)
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.
![wpf mvvm treeview example wpf mvvm treeview example](https://www.syncfusion.com/products/wpf/control/images/tree-view/wpf-treeview-multiselect-nodes.png)
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.
![wpf mvvm treeview example wpf mvvm treeview example](https://stevemonaco.github.io/assets/images/wpf-mvvm/MVVM-Flowchart-Large.png)
NET MAUI developer experience typically involves creating a user interface in XAML, and then adding code-behind that operates on the user interface.