C# – Best method for async initialization of view model in MVVM pattern (WPF)

asynccmultithreadingperformancewpf

I'm working on a business application (C#, WPF, EF, MVVM). I need to load a bunch of items from database, create view models for them and put them in a window. Is there a way to create the view model in another thread or do something similar to speed up UI?

The approximate average time needed to fetch all items from database = 1s
The approximate average time needed to instantiate all view models = 3s

I'm doing the first part through Loaded event of each item. but the second part is the bottleneck. any insight would be appreciated.

Best Answer

Break up the views into separate tabs/fly-outs etc and only populate these bits when the tabs/fly-outs are actually switched to.

Further to the above only populate the first element i.e. SELECT 1 only then populate the rest in the view on a scroll or drop down operation etc..

Lazy Loading.

In other words this is some of the layered caching alluded too and i do not see why the ViewModel has to have the data in advance as long as it goes off and gets it whenever requested..

Related Solutions

MVVM Reporting App – Data Access Layer Approach

You're definitely on the right track in making a Data Access Layer, although I would suggest making it more like a mysterious black box whose inner workings are unknown.

What I mean by this is your objects should be able to use the DAL to get/save objects, but they should have no idea how the data is actually obtained.

For example, instead of your ViewModel saying DAL.GetDataSet(someConnection, someQuery), you should call DAL.GetAccounts() which returns a list of AccountModel objects. The ViewModel should not care how or where the data is obtained from, only that it can magically get the objects it needs from the mysterious DAL object.

This keeps your data layer entirely separate, so if you ever need to change it out or adjust the queries, its all in one central location.

As a side note, your ViewModels should be the layer accessing the DAL. Models are simply dumb objects which contain data. They should have no advanced functionality, such as data access.

C# – How to make creating viewmodels at runtime less painful

The issue of dependencies when initiating a new view model can be handled with IOC.

public class MyCustomViewModel{
  private readonly IShoppingCartWebService _cartService;

  private readonly ITimeService _timeService;

  public ProductDTO ProductDTO { get; set; }

  public ProductDetailsViewModel(IShoppingCartWebService cartService, ITimeService timeService){
    _cartService = cartService;
    _timeService = timeService;
  }
}

When setting up the container...

Container.Register<IShoppingCartWebService,ShoppingCartWebSerivce>().As.Singleton();
Container.Register<ITimeService,TimeService>().As.Singleton();
Container.Register<ProductDetailsViewModel>();

When you need your view model:

var viewmodel = Container.Resolve<ProductDetailsViewModel>();
viewmodel.ProductDTO = myProductDTO;

When utilizing a framework such as caliburn micro there is often some form of IOC container already present.

SomeCompositionView view = new SomeCompositionView();
ISomeCompositionViewModel viewModel = IoC.Get<ISomeCompositionViewModel>();
ViewModelBinder.Bind(viewModel, view, null);

Best Answer

Related Solutions

MVVM Reporting App – Data Access Layer Approach

C# – How to make creating viewmodels at runtime less painful

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