在 WPF/CaliburnMicro/AutoFac 中创建通用 ViewModelFactory

Question

我有一个使用 Caliburn.Micro 和 AutoFac

的 WPF 应用程序

在 Bootstrapper.Configure() 中，我将我的视图和视图模型注册为：

protected override void Configure()
{
    var builder = new ContainerBuilder();
    //  register view models
    builder.RegisterAssemblyTypes(AssemblySource.Instance.ToArray())
        .Where(type => type.Name.EndsWith("ViewModel"))
        .AsSelf()
        .InstancePerDependency();
    //  register views
    builder.RegisterAssemblyTypes(AssemblySource.Instance.ToArray())
        .Where(type => type.Name.EndsWith("View"))
        .AsSelf()
        .InstancePerDependency();

    builder.Register<IWindowManager>(c => new WindowManager()).InstancePerLifetimeScope();

    _container = builder.Build();
}

    protected override IEnumerable<Assembly> SelectAssemblies()
{
    return new[]
    {
        typeof (MainViewModel).Assembly, // assembly that holds all the ViewModels
        typeof (MainView).Assembly // assembly that holds all the Views
    };
}

这很好用，视图和视图模型很好地按照此约定映射，例如。实例化 RandomViewModel 时，会显示 RandomView。

此外，我有很多 edit/list 派生自通用基础类的视图模型，其中通用类型是我解决方案中的实体。

例如，当我有实体 UserEntity、OrderEntity、AccountEntity 等时... 然后我会创建类:

//base classes
abstract class EditViewModelBase<T> : IEditViewModelBase where T: IEntity
abstract class ListViewModelBase<T> : IListViewModelBase where T: IEntity

//implementations
class UserEditViewModel : EditViewModelBase<UserEntity> {...}
class OrderEditViewModel : EditViewModelBase<OrderEntity> {...}
class AccountEditViewModel : EditViewModelBase<AccountEntity> {...}
...
class UserListViewModel : ListViewModelBase<UserEntity> {...}
class OrderListViewModel : ListViewModelBase<OrderEntity> {...}
class UserListViewModel : ListViewModelBase<UserEntity> {...}
...

现在我想创建一个 ViewModelFactory 以通用方式定位视图模型：

class ViewModelFactory
{
    public IEditViewModelBase CreateEditViewModel<T>()
    {
        //this method should do :
        // if typeof(T) == typeof(UserEntity) return new UserEditViewModel();
        // if typeof(T) == typeof(OrderEntity) return new OrderEditViewModel();
        // if typeof(T) == typeof(UserEntity) return new UserEditViewModel();
        ...
    }

    public IListViewModelBase CreateListViewModel<T>()
    {
        //this method should do :
        // if typeof(T) == typeof(OrderEntity) return new OrderListViewModel();
        ...
    }
}

我该如何解决这个问题，这样我就不必在每次向我的解决方案中添加新实体和 ViewModel 时都更改 ViewModelFactory？我正在考虑循环遍历容器，使用像 IsInstanceOf 和 Activator.CreateInstance 这样的反射技巧，但我无法让它工作...

Answer 1

我认为最简单的方法是使用内部使用 AutoFac 的 Auto Factory 库。你可以这样解决：

using AutoFactory;
class ViewModelFactory
{
    private IAutoFactory<IEditViewModelBase> _editFactory = Factory.Create<IEditViewModelBase>();
    private IAutoFactory<IListViewModelBase> _listFactory = Factory.Create<IListViewModelBase>();

    public IEditViewModelBase CreateEditViewModel<T>()
    {
        return _editFactory.SeekPart(t => t.BaseType.GetGenericArguments()[0].Name == typeof(T).Name);
    }

    public IListViewModelBase CreateListViewModel<T>()
    {
        return _listFactory.SeekPart(t => t.BaseType.GetGenericArguments()[0].Name == typeof(T).Name);
    }
}

或者如果你想直接用 AutoFac 做，你可以这样做：

using Autofac.Builder;
using Autofac.Features.Metadata
class ViewModelFactory
{
    private IContainer _container;
    private IEnumerable<Meta<Lazy<IEditViewModelBase>>> _editParts;

    public ViewModelFactory()
    {
        var builder = new ContainerBuilder();
        builder.RegisterAssemblyTypes(this.GetType().Assembly)
           .Where(t => typeof(IEditViewModelBase).IsAssignableFrom(t))
           .As<IEditViewModelBase>()
           .WithMetadata("type", t => t.BaseType.GetGenericArguments()[0]);
        _container = builder.Build();
        _editParts = _container.Resolve<IEnumerable<Meta<Lazy<IEditViewModelBase>>>>();
    }

    public IEditViewModelBase CreateEditViewModel<T>()
    {
        return _editParts.FirstOrDefault(p => p.Metadata["type"] as Type == typeof(T)).Value.Value;
    }
    ...
}

Answer 2

我觉得

public class Bootstrapper
{
  public IContainer Bootstrap()
  {
    var builder = new ContainerBuilder();

    builder.RegisterType<EventAggregator>().As<IEventAggregator>().SingleInstance();
    builder.RegisterType<MessageDialogService>().As<IMessageDialogService>();

    builder.RegisterType<FileDataService>().As<IDataService>();
    builder.RegisterType<fLookupProvider>().As<ILookupProvider<f>>();
    builder.RegisterType<fGroupLookupProvider>().As<ILookupProvider<fGroup>>();
    builder.RegisterType<fDataProvider>().As<IfDataProvider>();

    builder.RegisterType<fEditViewModel>().As<IfEditViewModel>();
    builder.RegisterType<NavigationViewModel>().As<INavigationViewModel>();
    builder.RegisterType<MainViewModel>().AsSelf();

    return builder.Build();
  }
}

在 WPF/CaliburnMicro/AutoFac 中创建通用 ViewModelFactory

Create a generic ViewModelFactory in WPF/CaliburnMicro/AutoFac

c#

generics

wpf

autofac

caliburn.micro