WF-全扫描(3)-补偿(B):


下面这篇博文转载自http://cnblogs.com/ 生鱼片的文章,这篇文章是基于WF3.5阐述的补偿的具体概念。在WF4.0中补偿又有了新的变化。从理解概念的角度,下面这篇文章很有启发意义:


以一个具体的例子来说明补偿是如果使用的,假如你计划要去旅游,那么你在出发前会先定火车票,然后在定酒店。那么如果你定到火车票了,可是当你去定酒店的时候你发现所有的酒店都已经被别人预定了,这个时候你定的火车票也没有用了,只好退订了。在我们的程序中我们用补偿来完成这个功能。下图是我们设计的工作流:


坚持学习WF(17):WF中的补偿 


假设我们有这样一个设计流程,首先预定火车票,然后在预定酒店,在预定酒店的时候我们会判断是否成功。如果不成功我们会抛出一个异常。在预定火车票活动(BookTicket)放到了CompensatableTransactionScopeActivity活动中,其中的补偿处理我们执行退订火车票的程序,如下图:


坚持学习WF(17):WF中的补偿


  在预定酒店的时候,如果预定不成功我们会使用上图中的BookFail(ThrowActivity)活动来抛出一个异常,下面是我们自定义的一个异常类,代码如下:


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.Serialization;
namespace CaryCompensationDemo
{
  [SerializableAttribute()]
  public class BookHotelException : Exception
  {
    public BookHotelException() : base()
    { }
    public BookHotelException(string message) : base(message)
    { }
    public BookHotelException(string message, Exception innerException)       : base(message, innerException)
    { }
    protected BookHotelException(SerializationInfo info, StreamingContext context)       : base(info, context)
    { }
  }
}


  在整个工作的错误处理程序中来捕获异常,并执行补偿处理,如下图:


坚持学习WF(17):WF中的补偿


我们使用CompensateActivity活动的TargetActivityName属性来指定对某个活动使用补偿。整个工作流的代码如下:


using System;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Collections;
using System.Drawing;
using System.Linq;
using System.Workflow.ComponentModel.Compiler;
using System.Workflow.ComponentModel.Serialization;
using System.Workflow.ComponentModel;
using System.Workflow.ComponentModel.Design;
using System.Workflow.Runtime;
using System.Workflow.Activities;
using System.Workflow.Activities.Rules;
namespace CaryCompensationDemo
{
  public sealed partial class CaryTourWorkflow: SequentialWorkflowActivity
  {
    public BookHotelException discontinuedProductException1 = new BookHotelException();
    public CaryTourWorkflow()
    {
      InitializeComponent();
    }
    private void TourStart_ExecuteCode(object sender, EventArgs e)
    {
      Console.WriteLine("准备去旅游咯");
    }
    private void BookTicket_ExecuteCode(object sender, EventArgs e)
    {
      Console.WriteLine("预定火车票");
    }
    private void CancelTicket_ExecuteCode(object sender, EventArgs e)
    {
      Console.WriteLine("退火车票");
    }
    private void BookHotelOK_ExecuteCode(object sender, EventArgs e)
    {
      Console.WriteLine("酒店预定成功");
    }
    private void BookOk_Condition(object sender, ConditionalEventArgs e)
    {
      e.Result = false;
    }
    private void BookHotelException_ExecuteCode(object sender, EventArgs e)
    {
      Console.WriteLine("没定到酒店");
    }
  }
}


 


三:使用补偿我们需要在宿主程序中加载持久化服务,下面是宿主程序的代码:


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Workflow.Runtime;
using System.Workflow.Runtime.Hosting;
namespace CaryCompensationDemo
{
  class Program
  {
    static AutoResetEvent waitHandle = new AutoResetEvent(false);
    static void Main()
    {
      using (WorkflowRuntime workflowRuntime = new WorkflowRuntime())
      {
        try
        {
          const string connectString = "Initial Catalog=workflowpersistence;
                       Data Source=localhost;Integrated Security=SSPI;";
        workflowRuntime.AddService(new SqlWorkflowPersistenceService(connectString));
          workflowRuntime.WorkflowCompleted += OnWorkflowCompleted;
          workflowRuntime.WorkflowTerminated += OnWorkflowTerminated;
          workflowRuntime.WorkflowAborted += OnWorkflowAborted;
          workflowRuntime.StartRuntime();
          Type type = typeof(CaryCompensationDemo.CaryTourWorkflow);
          workflowRuntime.CreateWorkflow(type).Start();
          waitHandle.WaitOne();
        }
        catch (Exception ex)
        {
          if (ex.InnerException != null)
            Console.WriteLine(ex.InnerException.Message);
          else
            Console.WriteLine(ex.Message);
        }
        finally
        {
          workflowRuntime.StopRuntime();
        }
      }
    }
    static void OnWorkflowAborted(object sender, WorkflowEventArgs e)
    {
      Console.WriteLine("请检查数据库连接是否异常");
      waitHandle.Set();
    }
    static void OnWorkflowCompleted(object sender, WorkflowCompletedEventArgs e)
    {
      Console.WriteLine("完成工作流");
      waitHandle.Set();
    }
    static void OnWorkflowTerminated(object sender, WorkflowTerminatedEventArgs e)
    {
      Console.WriteLine(e.Exception.Message);
      waitHandle.Set();
    }
  }
}


 


下面就可以运行得到执行程序:


坚持学习WF(17):WF中的补偿

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