先订阅后发布

private readonly IEventAggregator _eventAggregator;
public LoginViewModel(ILoginService iloginService, IEventAggregator eventAggregator)
{_iloginService = iloginService;_eventAggregator = eventAggregator;_eventAggregator.GetEvent<MessageEvent>().Subscribe(Reviced);UserName = "admin";PassWord = "123456";LoginCommand = new DelegateCommand<object>(DoLogin);}private void Reviced(string obj)
{throw new NotImplementedException();
}

 private readonly IEventAggregator _eventAggregator;public LeftMenuViewModel(IRegionManager regionManager, IUnityContainer unityContainer, IMenuService menuService, IEventAggregator eventAggregator){_eventAggregator = eventAggregator;_regionManager = regionManager;_menuService = menuService;origMenus = unityContainer.Resolve<GlobalValue>().UserInfo.Menus;var AllMenusList = menuService.GetAllMenus();var str = JsonHelper.SerializerToJsonString(AllMenusList);origMenus = JsonHelper.DeserializerJsonResult<List<SysMenu>>(str);eventAggregator.GetEvent<MessageEvent>().Publish("hello_ok");// 通过接口获取 菜单 数据   //origMenus = await menuBLL.GetMenus(0);// 通过接口获取 菜单 数据       // 需要初始化的进候进行菜单数据的获取填充// 通过Api接口//Task.Run(async () =>//{//    origMenus = unityContainer.Resolve<GlobalValue>().UserInfo.menus;//    origMenus = await menuBLL.GetMenus(0);// 通过接口获取 菜单 数据       //    unityContainer.Resolve<Dispatcher>().Invoke(() =>//    {//        this.FillMenus(Menus, 0);//    });//});FillMenus(Menus, 0);}

using Prism.Events;public class MessageEvent : PubSubEvent<string>
{}