如何使用 caliburn micro 在 Wpf 中注入 EF DbContext

Question

I try to build WPF application to interact with database through Repositories above Entity framework, and I use caliburn micro as MVVM framework

the problem is when I try to inject Repertories in ViewModels Through Simple Container it does not instantiate My DbContext

Repository

public class UserRepo : IUserRepo
{
    private AppDb _ctx;

    public UserRepo(AppDb ctx)
    {
            _ctx = ctx;
    }
}

application context

public class AppDb : DbContext
{
    public AppDb(DbContextOptions options) : base(options)
    {
    }

    public DbSet<User> Users { get; set; }
}

configuration on Simple Container

class Bootstrapper : BootstrapperBase
{

    private SimpleContainer _container = new SimpleContainer();
    private AppDb _db;
    public Bootstrapper()
    {
        Initialize();

        var options = new DbContextOptionsBuilder<AppDb>()
                      .UseSqlServer(@"Server=(localdb)\MSSQLLocalDB;Database=XRaySystem;Integrated Security=True;")
                      .Options;

        _db = new AppDb(options);
    }

    protected override void Configure()
    {
        _container.Instance(_container);

        _container
            .Singleton<IWindowManager, WindowManager>()
            .Singleton<IEventAggregator, EventAggregator>();
        //register the DataContext
        // i don't know how to add it
        _container.RegisterInstance(typeof(AppDb), null, _db); // <<<<<<<<<< how to add this correctly 
        //Register Reporisotries
        _container
            .PerRequest<IUserRepo, UserRepo>();
        //Register ViewModels
        GetType().Assembly.GetTypes()
            .Where(type => type.IsClass)
            .Where(type => type.Name.EndsWith("ViewModel"))
            .ToList()
            .ForEach(viewModelType => _container.RegisterPerRequest(
                viewModelType, viewModelType.ToString(), viewModelType));
    }
    protected override void OnStartup(object sender, StartupEventArgs e)
    {


        DisplayRootViewFor<DashBoardViewModel>();
        //base.OnStartup(sender, e);
    }

    protected override object GetInstance(Type service, string key)
    {
        return _container.GetInstance(service, key);
    }

    protected override IEnumerable<object> GetAllInstances(Type service)
    {
        return _container.GetAllInstances(service);
    }


    protected override void BuildUp(object instance)
    {
        _container.BuildUp(instance);
    }
}

View model

class DoctorViewModel : Screen
{
    private readonly IUserRepo _userRepo;

    public DoctorViewModel(IUserRepo userRepo)
    {
        _userRepo = userRepo;
    }
}

UserRepo is instantiated but with null AppDb

my Question

How to configure Simple Container to Add AppDb to UserRepo ?

I have reproduced the same problem in on GitHub

Answer 1

After some debugging, I found that Configure Method run first then the constructor call !! So the instantiation is happened after the Configuration already done with null

I solve it by adding the instantiation of _db in Configure method itself

class Bootstrapper : BootstrapperBase
{

    private SimpleContainer _container = new SimpleContainer();
    private AppDb _db;
    public Bootstrapper()
    {
        Initialize();
    }

    protected override void Configure()
    {
        var options = new DbContextOptionsBuilder<AppDb>()
                     .UseSqlServer(@"Server=(localdb)\MSSQLLocalDB;Database=XRaySystem;Integrated Security=True;")
                     .Options;

        _db = new AppDb(options); //<<<< solve the problem

        _container.Instance(_container);

        _container
            .Singleton<IWindowManager, WindowManager>()
            .Singleton<IEventAggregator, EventAggregator>();
        //register the DataContext
        _container.Instance(_db);
        // _container.RegisterInstance(typeof(AppDb), null, _db); 
        
         //Register Reporisotries
         _container
            .PerRequest<IUserRepo, UserRepo>();
        //Register ViewModels
        GetType().Assembly.GetTypes()
            .Where(type => type.IsClass)
            .Where(type => type.Name.EndsWith("ViewModel"))
            .ToList()
            .ForEach(viewModelType => _container.RegisterPerRequest(
                viewModelType, viewModelType.ToString(), viewModelType));
    }
    protected override void OnStartup(object sender, StartupEventArgs e)
    {

        DisplayRootViewFor<DashBoardViewModel>();
        //base.OnStartup(sender, e);
    }

    protected override object GetInstance(Type service, string key)
    {
        return _container.GetInstance(service, key);
    }

    protected override IEnumerable<object> GetAllInstances(Type service)
    {
        return _container.GetAllInstances(service);
    }


    protected override void BuildUp(object instance)
    {
        _container.BuildUp(instance);
    }
}