void ExecuteLoadCommand()
{
      //TaskExtension for async void Command 
      ALongTask().Await( completedCallback:() =>
      {
          this.AllMedicines.AddRange(_medicineSerivce.GetAllMedicines());
      }, errorCallback:null,configureAwait:true);
}

该方式执行效果和之前一样，而且不用在void方法加上async 和方法内部await就能实现异步等待操作，而这只是推荐在Command的Excuted Method使用，这也是官方推荐的，因为一般Excuted Method返回值只会是void

二.回答一些问题

如何在Prism使用AOP？

?其实AOP并不是属于prism特有的功能，但是由于prism支持扩展IOC容器：Unity和DryIoc，只要其IOC容器本身支持，那就可以，由于默认Prism是以Unity为默认IOC容器，所以以Unity为例子：

1. NuGet引用Unity AOP库：Unity.Interception(最新是5.11.1)

2. 在App.cs添加扩展AOP，代码如下：

    protected override void RegisterTypes(IContainerRegistry containerRegistry)
    {
        var container = PrismIocExtensions.GetContainer(containerRegistry);
        container.AddNewExtension<Interception>()//add Extension Aop
                   //注册服务和添加显示拦截
            .RegisterType<IMedicineSerivce, MedicineSerivce>(new Interceptor<InterfaceInterceptor>(), new InterceptionBehavior<PolicyInjectionBehavior>())
            .RegisterType<IPatientService, PatientService>(new Interceptor<InterfaceInterceptor>(), new InterceptionBehavior<PolicyInjectionBehavior>())
             .RegisterType<IUserService, UserService>(new Interceptor<InterfaceInterceptor>(), new InterceptionBehavior<PolicyInjectionBehavior>());
   
    }
   

3. 新建类LogHandler继承ICallHandler用于处理拦截逻辑和特性LogHandlerAttribute,模拟记录Log，:

   public class LogHandler : ICallHandler
   {
       public int Order { get ; set ; }
   
       public IMethodReturn Invoke(IMethodInvocation input, GetNextHandlerDelegate getNext)
       {
             Debug.WriteLine("-------------Method Excute Befored-------------");
             Debug.WriteLine($"Method Name:{input.MethodBase.Name}");
             if (input.Arguments.Count>0)
             {
                 Debug.WriteLine("Arguments:");
                 for (int i = 0; i < input.Arguments.Count; i++)
                 {
                     Debug.WriteLine($"parameterName:{input.Arguments.ParameterName(i)},parameterValue:{input.Arguments[i]}");
                 }
             }           
             var methodReturn = getNext()(input, getNext);
             Debug.WriteLine("-------------Method Excute After-------------");
             if (methodReturn.Exception!=null)
             {
                 Debug.WriteLine($"Exception:{methodReturn.Exception.Message} \n");
             }
             else
             {
                 Debug.WriteLine($"Excuted Successed \n");
             }
             return methodReturn;
       }
   }
   
   
   public class LogHandlerAttribute : HandlerAttribute
   {
       public override ICallHandler CreateHandler(IUnityContainer container)
       {
           return new LogHandler() { Order = this.Order };
       }
    }
   

4. 为那些需要拦截的接口标上Attribute

       [LogHandler]
       public interface IMedicineSerivce
       {
           List<Medicine> GetAllMedicines();
           List<Recipe> GetRecipesByPatientId(int patientId);
       }
       [LogHandler]
       public interface IPatientService
       {
           List<Patient> GetAllPatients();
       } 
       [LogHandler]
       public interface IUserService
       {
           List<User> GetAllUsers();
       }
   
   

   效果如下:

Vs输出:

-------------Method Excute Befored-------------
Method Name:GetAllMedicines
-------------Method Excute After-------------
Excuted Successed 

-------------Method Excute Befored-------------
Method Name:GetRecipesByPatientId
Arguments:
parameterName:patientId,parameterValue:1
-------------Method Excute After-------------
Excuted Successed 

-------------Method Excute Befored-------------
Method Name:GetRecipesByPatientId
Arguments:
parameterName:patientId,parameterValue:2
-------------Method Excute After-------------
Excuted Successed 

-------------Method Excute Befored-------------
Method Name:GetRecipesByPatientId
Arguments:
parameterName:patientId,parameterValue:3
-------------Method Excute After-------------
Excuted Successed 

-------------Method Excute Befored-------------
Method Name:GetRecipesByPatientId
Arguments:
parameterName:patientId,parameterValue:4
-------------Method Excute After-------------
Excuted Successed