基於微軟並行計算的工作流程解決方案 (2) Tasked based Parallel Activity

上一節我們做了個簡單的測試證明了Parallel並不是真正意義上的並行工作流程，並且分析了它的缺陷。

在.net framework 4裡面有很多關於並行計算的組件，現在我們就要利用微軟TPL(The Task Parallel Library)中的System.Threading.Tasks.Task類型來實現並行的分支。要定製非同步工作流程活動，我們的新類必須繼承於.net WF中的基類AsyncCodeActivity

我們重寫一下PartDBReplicationActivity,

public class PartDBReplicationAsyncActivity : AsyncCodeActivity
{
        public InOutArgument<Order> OrderInActivity { get; set; }

        protected override IAsyncResult BeginExecute(AsyncCodeActivityContext context, AsyncCallback callback, object state)
        {
            Order order = context.GetValue(OrderInActivity);
            Task worker = Task.Factory.StartNew(
                (o) =>
                {
                    order.Status = OrderStatus.InProcess;
                    //Call Part service
                    Thread.Sleep(5000);
                }, state);
            worker.ContinueWith(task => callback(task));
            return worker;
        }

        protected override void EndExecute(AsyncCodeActivityContext context, IAsyncResult result)
        {
           
        }
}

再看新的VehicleReplicationAsyncActivity 

public class VehicleReplicationAsyncActivity : AsyncCodeActivity
 {
        public InOutArgument<Order> OrderInActivity { get; set; }

        protected override IAsyncResult BeginExecute(AsyncCodeActivityContext context, AsyncCallback callback, object state)
        {
            //Console.WriteLine("VehicleDBReplication AsyncActivity starts at:{0} \r\n", DateTime.Now.ToString());
            Order order = context.GetValue(OrderInActivity);
            Task worker = Task.Factory.StartNew(
                (o) =>
                {                  
                    order.Status = OrderStatus.InProcess;
                    //Call Part service
                    Thread.Sleep(5000);
                    //Console.WriteLine("VehicleDBReplication AsyncActivity ends at {0}.\r\n", DateTime.Now.ToString());
                }, state);
            worker.ContinueWith(task => callback(task));
            return worker;
        }

        protected override void EndExecute(AsyncCodeActivityContext context, IAsyncResult result)
        {

        }
 }

我們修改main裡面的代碼讓它執行新的Close Order流程

class Program
 {
static void Main(string[] args)
        {
            DateTime dtStart = DateTime.Now;
            Console.WriteLine("CloseOrder workflow starts at:{0}", dtStart);
            Console.WriteLine("--------------------------------------------------------------");
//WorkflowInvoker.Invoke(new CloseOrderWorkflow());
            WorkflowInvoker.Invoke(new CloseOrderParallelWorkflow());
            Console.WriteLine("--------------------------------------------------------------");
            DateTime dtEnd = DateTime.Now;
            Console.WriteLine("CloseOrder workflow ends at:{0}", dtEnd.ToString());
            Console.WriteLine("Total time elapsed in seconds :{0}",( dtEnd - dtStart).Seconds.ToString());
            Console.Read();
        }
 }

看結果

現在整個流程只花了5秒鐘，我們初步完成基於微軟並行解決方案的並行工作流程。

至此我們實現的並發工作流程要求分支之間安全執行緒，業務上沒有耦合和次序關係。

我們實現的基於並行計算並發工作流程活動也存在一些缺陷：可擴充性不高，開發人員過於底層細節的關注，封裝性不好等等..

後面的任務是要完成一個真正意義上的可擴充的並發Parallel Activity，使用者只要拖拽這個工作流程活動到Visual Studio裡面，設定一些參數，比如綁定處理的真正任務，那麼就無需和Parallel.Task底層對象打交道，只需要對商務邏輯的實現。 

範例程式碼：

http://files.cnblogs.com/huyq2002/ParallelTask.zip