Mvvm Light和Entity Framework核心最佳实践

Question

I'm creating a new UWP application using Mvvm Light and Entity Framework Core. I'm new to these 2 technologies.

I create my model : the Article class is a simple ObservableObject with 3 properties : Id , Référence and Désignation .

My DbContext is the following :

public class UniversalTest1Context : DbContext
{
    public DbSet<Article> Articles { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlite("Filename=UniversalTest1.db");
    }

}

I'm looking for the best way to manage the DbContext and my different views.

Is it better to create one DbContext for the whole application ? I don't really like that idea .

Do I have to create a DbContext in each ViewModel ? I like this more .
When the user double tap an item in the article list view, I navigate to the article detail view and pass the article to the view model associated to the article detail view. But this already existing article is not related to the DbContext of the Article detail view model.

Is it possible to instantiate the DbContext only when needed ? My prefered option .
For this, I pass the article from the list view model to the detail view model. And then, when the user clicks save I execute something like this :

using (var db = new UniversalTest1Context())
{
    db.Articles.Add(article);
    await db.SaveChangesAsync();
}

Of course, this works for new articles (insert), but not for existing ones (update).

I have difficulties making up my mind here.

Many thanks in advance, Julien

Answer 1

In my opinion, you should hide all storing operations by interface (like IArticleRepo or smth like that) and you should use IoC for accessing it (if some class wants to work with Store, it have to declare IArticleRepo in ctor parameters). Also, inside this interface IArticleRepo you can delcare neecessarry operations with Articles, like IArticleRepo.AddArticle(Article a). If you do so, you can choose later, whether you want to create dbcontext for each operation or not OR maybe you want to make IArticleRepo implementation as singletone using IoC container. But such decisions should not affect on other code. As very simle sample in my code (I showing only this file, whole project is ugly and I will change it) https://github.com/tym32167/arma3beclient/blob/master/src/Arma3BE.Client.Libs/Repositories/PlayerRepository.cs#L23