MVVM (Model-View-ViewModel) Architecture Questions and Answers for Viva

Answer-1: MVVM (Model-View-ViewModel) is a design pattern that separates the UI (View) from business logic (Model) by introducing a ViewModel, which acts as a mediator.

Answer-2: The Model represents the application's data, logic, and business rules. It communicates with the database or API.

Answer-3: The View represents the UI layer, displaying data and interacting with the user. It is bound to the ViewModel for automatic UI updates.

Answer-4: The ViewModel acts as a bridge between the View and the Model, handling UI logic and data binding to ensure a clean separation of concerns.

Answer-5: MVVM introduces a ViewModel to handle UI logic and binding, whereas MVC relies on the Controller for handling input and interaction between the Model and View.

Answer-6: MVVM was introduced by Microsoft, particularly for WPF and Silverlight development.

Answer-7: MVVM supports data binding, which simplifies UI updates and enhances testability by separating UI logic from business logic.

Answer-8: Examples include WPF, Xamarin, Angular (with RxJS), and Knockout.js.

Answer-9: By separating UI logic (ViewModel) from the View, MVVM allows developers to unit test ViewModels without requiring the UI layer.

Answer-10: Advantages include enhanced separation of concerns, better testability, support for data binding, and reduced code redundancy.

Answer-11: Disadvantages include increased complexity for simple applications and a steeper learning curve for beginners.

Answer-12: Data binding is a technique where the View automatically updates to reflect changes in the ViewModel's properties and vice versa.

Answer-13: One-way binding updates the View from the ViewModel, while two-way binding allows changes in the View to propagate back to the ViewModel.

Answer-14: MVVM promotes DRY by reusing ViewModels across different Views and centralizing UI logic in a single place.

Answer-15: ICommand is an interface in MVVM used to bind UI actions (like button clicks) to methods in the ViewModel.

Answer-16: MVVM uses commands and property bindings to manage events, avoiding direct event handling in the View.

Answer-17: In MVVM, the ViewModel handles data binding and UI logic, while in MVP, the Presenter handles interaction between the Model and View without data binding.

Answer-18: MVVM?s separation of concerns and modularity allow for scaling individual components independently.

Answer-19: Tools like Prism, Caliburn.Micro, and MVVMLight are commonly used for implementing MVVM in WPF applications.

Answer-20: User input is processed through commands or property bindings in the ViewModel, which then updates the Model or performs necessary actions.

Answer-21: Key challenges include complexity in managing bindings, increased boilerplate code, and a learning curve for beginners.

Answer-22: Yes, MVVM is widely used in mobile app frameworks like Xamarin.Forms and MAUI due to its suitability for data binding and separation of concerns.

Answer-23: MVVM manages state in the ViewModel, ensuring the UI reflects the current state through data binding.

Answer-24: The Command pattern encapsulates requests (e.g., button clicks) into objects, allowing for parameterization, queuing, and logging.

Answer-25: Examples include modern desktop apps built with WPF, mobile apps using Xamarin, and Angular-based SPAs.

Answer-26: ObservableCollection is a data structure in .NET that notifies the View when the collection changes, making it ideal for use in MVVM data binding.

Answer-27: MVVM promotes reuse by allowing the same ViewModel to be shared across different Views and by encapsulating UI logic separately.

Answer-28: Dependency Injection in MVVM facilitates loose coupling by injecting services or dependencies into ViewModels, improving testability and modularity.

Answer-29: Yes, MVVM can be implemented in web applications using frameworks like Knockout.js, Angular, and Vue.js, which support the ViewModel concept.

Answer-30: MVVM simplifies debugging by isolating UI logic in the ViewModel and maintaining clear boundaries between layers, making maintenance easier.

Answer-31: Property notification is implemented using INotifyPropertyChanged, enabling the View to react to changes in the ViewModel's properties.

Answer-32: MVVM handles multi-threading by using mechanisms like Task-based Asynchronous Patterns (TAP) or async/await, ensuring the UI thread remains responsive.

Answer-33: Converters in MVVM transform data between the ViewModel and the View, ensuring proper formatting or transformation for display.

Answer-34: While MVVM is designed for data binding, it can technically work without it, though it loses much of its advantage in simplifying UI updates.

Answer-35: MVVM supports localization by maintaining language resources in the Model and binding them to UI elements through the ViewModel.

Answer-36: Attached properties are a way to add custom behaviors to UI elements in XAML, often used in MVVM for binding custom logic to Views.

Answer-37: MVVM handles validation by implementing interfaces like IDataErrorInfo or INotifyDataErrorInfo in the ViewModel to notify the View about validation errors.

Answer-38: RaisePropertyChanged notifies the View of property changes in the ViewModel, enabling UI updates.

Answer-39: Navigation in MVVM is managed by using navigation services or commands in the ViewModel to control which View is displayed.

Answer-40: MVVM adheres to the Single Responsibility Principle by assigning each component (Model, View, ViewModel) a distinct role, ensuring separation of concerns.

Answer-41: BindingContext is used in Xamarin.Forms, while DataContext is used in WPF. Both specify the object to which UI elements bind in MVVM.

Answer-42: MVVM uses property change notifications and data bindings to track dependencies between the ViewModel and the View, ensuring consistency.

Answer-43: Yes, MVVM can work with REST APIs by using the Model to fetch data and the ViewModel to process and expose it to the View.

Answer-44: Binding modes (e.g., OneWay, TwoWay) define the direction of data flow between the View and ViewModel, allowing flexibility in interaction.

Answer-45: MVVM promotes loose coupling by separating concerns into distinct layers and using binding instead of direct references between components.

Answer-46: Behaviors in MVVM extend the functionality of UI elements by attaching reusable custom logic, enhancing flexibility without modifying the View.

Answer-47: Xamarin.Forms uses MVVM with features like data binding, Command patterns, and frameworks like Prism or MVVMLight for efficient implementation.

Answer-48: MVVM's separation of concerns makes it easier to use the same ViewModel across multiple platforms, such as mobile, desktop, and web.

Answer-49: Performance can be optimized by using efficient binding, reducing UI redraws, and leveraging asynchronous programming in the ViewModel.

Answer-50: Error handling in MVVM is typically managed in the ViewModel, using try-catch blocks or exposing error states to the View through bindings.