如何在 Prism 的 运行 时间注入新实例?

How to inject new instance at run time in Prism?

我正在为 WPF 应用程序使用 Prism 7.1。 我尝试使用内置的 IOC(Unity),但我不知道如何在 运行 时间从方法或 containerProvider 解析新实例。但似乎无法将 IContainerProvider 注入到我的视图模型中。我有什么选择吗?

我想重新加载我的数据库上下文。有人告诉我创建新上下文是最简单的。

    public class ProjectViewModel : BindableBase
    {
        private UnitOfWork unitOfWork;
        private IContainerProvider containerProvider;
        private IEventAggregator eventAggregator;
        #region Constructor
        public ProjectViewModel(UnitOfWork unitOfWork, IContainerProvider cp, IEventAggregator ea)
        {
            this.unitOfWork = unitOfWork;
            containerProvider = cp;
            eventAggregator = ea;
            eventAggregator.GetEvent<SendReloadDataEvents>().Subscribe(Reload);
            Reload();
        }
        #endregion

        private void Reload()
        {
            this.unitOfWork = containerProvider.Resolve<UnitOfWork>();
            Projects = new ObservableCollection<Projects>(unitOfWork.ProjectRepo.GetAll());
            Customers = new ObservableCollection<Customers>(unitOfWork.CustomerRepo.Find(x => x.Projects.Count > 0));
            SelectedProjectType = null;
        }
//Other logic continues
}

注入容器是一种反模式,所以我们会尽量避免这种情况,而是注入一个工厂。事实上,IContainerProviderIContainerRegistry 并没有因为这个原因自行注册,因此无法注入它们。

虽然工厂很容易:

public class ProjectViewModel : BindableBase
{
    private UnitOfWork unitOfWork;
    private Func<UnitOfWork> unitOfWorkFactory;
    private IEventAggregator eventAggregator;
    #region Constructor
    public ProjectViewModel(Func<UnitOfWork> unitOfWorkFactory, IEventAggregator ea) // no need to inject a unit of work
    {
        _unitOfWorkFactory = unitOfWorkFactory;
        eventAggregator = ea;
        ea.GetEvent<SendReloadDataEvents>().Subscribe(Reload); // prefer the parameter
        Reload();
    }
    #endregion

    private void Reload()
    {
        this.unitOfWork = _unitOfWorkFactory(); // create a new one here (the container does the work but is hidden)
        Projects = new ObservableCollection<Projects>(unitOfWork.ProjectRepo.GetAll()); // I'd rather update the existing collection
        Customers = new ObservableCollection<Customers>(unitOfWork.CustomerRepo.Find(x => x.Projects.Count > 0)); // same here, or probably, it could just be IEnumerable
        SelectedProjectType = null;
    }
//Other logic continues
}

请注意,此 Func<> 工厂仅适用于最简单的情况。如果您需要将参数传递到产品构造函数中,则必须按照 所述自行编写代码。还要注意容器如何永远不会出现在任何地方(除了配置它的地方),让你的代码依赖于容器是不必要的,并且会使测试更难看。