DisplayRootViewFor<> 上的 NullReferenceException [重复]答案

【问题标题】：NullReferenceException on DisplayRootViewFor<> [duplicate]DisplayRootViewFor<> 上的 NullReferenceException [重复]
【发布时间】：2017-06-05 15:18:41
【问题描述】：

我创建了一个派生自BootstrapperBase 的类，覆盖OnStartup() 并调用DisplayRootViewFor<AppViewModel>()，就像在文档中一样。

但是当我启动应用程序时，我在DisplayRooViewFor<AppViewModel>() 上得到一个NullReferenceException

using Caliburn.Micro;
using MHBRestore.Logic;
using MHBRestore.UI.ViewModel;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;

namespace MHBRestore.UI
{
public class AppBootstrapper : BootstrapperBase
{
    private SimpleContainer _container = new SimpleContainer();

    public AppBootstrapper()
    {
        Initialize();
    }

    protected override void OnStartup(object sender, StartupEventArgs e)
    {
        DisplayRootViewFor<AppViewModel>();
    }

    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);
    }
}
}

【问题讨论】：

标签： c# wpf visual-studio caliburn.micro

【解决方案1】：

尝试覆盖Configure 方法并注册您的视图模型类型：

public class AppBootstrapper : BootstrapperBase
{
    private SimpleContainer _container = new SimpleContainer();

    public AppBootstrapper()
    {
        Initialize();
    }

    protected override void Configure()
    {
        _container.Singleton<IWindowManager, WindowManager>();
        _container.Singleton<IEventAggregator, EventAggregator>();
        _container.RegisterPerRequest(typeof(AppViewModel), null, typeof(AppViewModel));
    }

    protected override void OnStartup(object sender, StartupEventArgs e)
    {
        DisplayRootViewFor<AppViewModel>();
    }

    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);
    }
}

【讨论】：