学习<>WF程序队列应用实例－Wait活动

1.Wait活动首先等待一段指定的时间的流逝,然后在完成.代码如下:

using System;
using System.Collections.Generic;
using System.Text;
using System.Workflow.ComponentModel;
using System.Workflow.Runtime;

namespace Goyier.Activities
{
       public class Wait : Activity
    {
        private Guid timerId;

        public static readonly DependencyProperty DurationProperty = DependencyProperty.Register("Duration", typeof(TimeSpan), typeof(Wait));
        //等待时间间隔
        public TimeSpan  Duration
        {
            get
            {
                return(TimeSpan) base.GetValue(DurationProperty);
            }
            set
            {
                base.SetValue(DurationProperty, value);
            }
        }

        protected override ActivityExecutionStatus Execute(ActivityExecutionContext executionContext)
        {
            WorkflowQueuingService qservice = executionContext.GetService<WorkflowQueuingService>();
            timerId = Guid.NewGuid();
            WorkflowQueue queue = qservice.CreateWorkflowQueue(timerId, true);
            queue.QueueItemAvailable+=new EventHandler<QueueEventArgs>(this.ContinueAt);
            //自定的计时器服务
            TimerService timerService = executionContext.GetService<TimerService>();
            timerService.SetTime(timerId,Duration);
            Console.WriteLine(Duration);
            return ActivityExecutionStatus.Executing;
        }

        void ContinueAt(object sender,QueueEventArgs  e)
        {
            ActivityExecutionContext context = sender as ActivityExecutionContext;
            WorkflowQueuingService qservice = context.GetService<WorkflowQueuingService>();
            WorkflowQueue queue = qservice.GetWorkflowQueue(timerId);
            qservice.DeleteWorkflowQueue(timerId);
            context.CloseActivity();
        }
    }
}

这个自定义的Wait活动依赖TimerService的实现,TimerServices管理着实际的计时器,在Wait活动的Execute方法中,创建一个WF程序队列并注册了ContinueAt方法,随后调用TimerServices的SetTimer方法,将一个代表计时器的Uid传入方法,当计时器被触发时,TimerServices会把数据压入Wait活动创建的WF程序队列中,当调度器调用ContinueAt方法,并迁移到Closed状态.

2.我们现在定义一个名TimerServices的抽象类,以便为我们的计时器服务提供接口.我们可以实现各种各样的逻辑,代码如下:

using System;
using System.Collections.Generic;
using System.Text;
using System.Workflow.ComponentModel;
using System.Workflow.Runtime;

namespace Goyier.Activities
{
public abstract class TimerService
    {
        public abstract void SetTime(Guid timerId, TimeSpan duration);
        public abstract void CancelTime(Guid timeerId);
    }
}

3.接下来我们实现一个简单的计时器服务,代码如下:

using System;
using System.Collections.Generic;
using System.Text;
using System.Workflow.ComponentModel;
using System.Workflow.Runtime;
using System.Threading;
using Goyier.Activities

namespace Goyier.Services
{
   public class SimpleTimerService : TimerService
    {
        WorkflowRuntime runtime;
        Dictionary<Guid, Timer> timers = new Dictionary<Guid, Timer>();
        public SimpleTimerService(WorkflowRuntime runtime)
        {
            this.runtime = runtime;
        }
        //设置计时器
        public override void SetTime(Guid timerId, TimeSpan duration)
        {
            Guid instanceId = WorkflowEnvironment.WorkflowInstanceId;
            Timer timer = new Timer(delegate(object o)
                                             {
                                                 WorkflowInstance instance = runtime.GetWorkflow(instanceId);
                                                 instance.EnqueueItem(timerId, null, null, null);
                                             }, timerId, duration, new TimeSpan(Timeout.Infinite));
            timers.Add(timerId, timer);
        }

        //取消计时器
        public override void CancelTime(Guid timerId)
        {
           ((IDisposable)timers[timerId]).Dispose();
           timers.Remove(timerId);
        }
    }
}

4.接下来我们在Wait活动所在的程序集的元数据里加入以下元数据:

[assembly: XmlnsDefinition("http://GuoyiWF/Activities", "Goyier.Activities")]

以便将XML名称空间"http://GuoyiWF/Activities"映射到CLR名称空间"Guoyier.Activities".

5.我们新建一个顺序工作控制台应用程序,来进行测试,在项目中新建一个xoml文件,内容如下:

<Wait x:Name="mywait" xmlns="http://GuoyiWF/Activities" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Duration="00:00:10"> </Wait>

等待的时间间隔设置为10秒钟

6.执行Wait活动的代码如下: