How to manage view models in viewports?

Question

How to manage view models in viewports?

fatih uyanık 225

Hello

I'm trying to learn the ViewModel pattern. I want to ask you about a subject that I cannot understand.

I am implementing Dependency Injection using the Microsoft.Extensions package. I recorded the database and message services I use. So far, no problem.

In my project I have view models that manage views. In some sources, it is recommended to register all these as services at the beginning of the application and use them through dependency. This doesn't seem right to me in terms of performance. The correct approach would be to save these view models as services or to manage them dynamically by creating instances through a central navigation class. Finally, use the navigation class by registering it as a service.

Can you guide me on this?

Thanks.

Hui Liu-MSFT 48,681 Reputation points Microsoft External Staff

2023-12-07T05:59:38.9766667+00:00
Hi,@fatih uyanık.Welcome to Microsoft Q&A Forum.

Not sure about your specific project content. You could try to refer to the following description.

The approach to managing ViewModels in a WPF application using the MVVM (Model-View-ViewModel) pattern can vary based on the size and complexity of your application. Both the approaches you mentioned are valid, and the choice between them often depends on the specific requirements and design preferences of your application.

1. Registering View Models as Services:

Pros:

Consistency: All your ViewModels are registered in a central place, promoting consistency and making it easier to manage dependencies.

Ease of Dependency Injection: ViewModels can be injected into other services, making it easier to achieve loose coupling.

Cons:

May result in increased memory consumption if all view models are instantiated at the beginning.

Might not be suitable for large applications with numerous view models.

// Example registration of view models in Startup.cs services.AddSingleton<MainViewModel>(); services.AddSingleton<DetailsViewModel>();

2.Dynamic View Model Creation:

Pros:

Allows for on-demand creation of view models, potentially saving resources. Suitable for applications with a large number of view models. Cons: Adds complexity in managing the creation and disposal of view models. May require a centralized navigation or factory class.

public class ViewModelFactory { private readonly IServiceProvider serviceProvider; public ViewModelFactory(IServiceProvider serviceProvider) { this.serviceProvider = serviceProvider; } public T CreateViewModel<T>() where T : class { return serviceProvider.GetService<T>(); } }

3.Using a Navigation Service: Pros: Centralizes navigation logic. Can be combined with dynamic view model creation. Cons: Introduces an additional layer of abstraction. Requires careful design to avoid potential pitfalls.

public class NavigationService { private readonly IServiceProvider serviceProvider; public NavigationService(IServiceProvider serviceProvider) { this.serviceProvider = serviceProvider; } public void Navigate<TViewModel>() where TViewModel : class { var viewModel = serviceProvider.GetService<TViewModel>(); // Perform navigation logic... } }

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