C#并行IO完成端口

Question

我正在尝试找出等待一定数量的 I/O 完成端口完成的最佳方法。

对于这种情况，假设我在 MVC3 网络应用程序中。 (我的理解是这里建议使用 I/O 完成端口，这样我可以将原始线程返回到 IIS 以服务其他请求)

假设我有一个 ID 数组，我想从某个网络调用中为每个 ID 获取一个对象。

并行化这种同步方法的最佳方式是什么？

   public class MyController: Controller
   {
       public ActionResult Index(IEnumerable<int> ids)
       {
            ids.Select(id => _context.CreateQuery<Order>("Orders")
                                     .First(o => o.id == id));
            DataServiceQuery<Order> query = _context.CreateQuery<Order>("Orders");
            return Json(query);
       }

       private DataServiceContext _context; //let's ignore how this would be populated
   }

我知道它会这样开始:

   public class MyController: AsyncController
   {
       public void IndexAsync(IEnumerable<int> ids)
       {
            // magic here...

            AsyncManager.Sync(() => AsyncManager.Parameters["orders"] = orders);
       }

       public ActionResult IndexCompleted(IEnumerable<Order> orders)
       {
            return Json(orders);
       }

       private DataServiceContext _context; //let's ignore how this would be populated
   }

我应该使用 DataServiceContext.BeginExecute 吗？方法？ DataServiceContext.BeginExecuteBatch ？我使用的数据服务一次只能获取一条记录(这是我无法控制的)，我希望这些单独的查询并行运行。

Answer 1

这是我最终用于在 MVC3 中运行一批异步操作的模式:

public class MyController: AsyncController
   {
       public void IndexAsync(int[] ids)
       {
            var orders = new Orders[ids.Length];
            AsyncManager.Parameters["orders"] = orders;

            // tell the async manager there are X operations it needs to wait for
            AsyncManager.OutstandingOperations.Increment(ids.Length);

            for (int i = 0; i < ids.Length; i++){
               var index = i; //<-- make sure we capture the value of i for the closure

               // create the query
               var query = _context.CreateQuery<Order>("Orders");

               // run the operation async, supplying a completion routine
               query.BeginExecute(ar => {
                   try {
                       orders[index] = query.EndExecute(ar).First(o => o.id == ids[index]);
                   }
                   catch (Exception ex){
                       // make sure we send the exception to the controller (in case we want to handle it)
                       AsyncManager.Sync(() => AsyncManager.Parameters["exception"] = ex);
                   }
                   // one more query has completed
                   AsyncManager.OutstandingOperations.Decrement();
               }, null);
            }
       }

       public ActionResult IndexCompleted(Order[] orders, Exception exception)
       {
            if (exception != null){
                throw exception; // or whatever else you might like to do (log, etc)
            }
            return Json(orders);
       }

       private DataServiceContext _context; //let's ignore how this would be populated
   }