Question

我正在试图找出等待一些I / O完成端口完成的最佳方法。

对于这种情况，假设我在一个MVC3网络应用程序中。（我的理解是建议使用I / O完成端口，这样我就可以将原始线程返回给IIS来为其他请求服务）

假设我有一系列ID，我想从某个网络呼叫中获取每个ID的对象。

并行化此同步方法的最佳方法是什么？

   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
   }

我知道它会像这样开始：

   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方法吗？ DataServiceContext.BeginExecuteBatch？我正在使用的数据服务一次只能获得一条记录（这超出了我的控制范围），我希望这些单独的查询能够并行运行。

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
   }

Answer 2

使用TPL非常简单。

public ActionResult Index(IEnumerable<int> ids)
{
    var result = ids.AsParallel()
      .Select(id => GetOrder(id))
      .ToList();
    return Json(result);
}

Order GetOrder(int id) { ... }

c＃并行IO完成端口

2 个答案: