Q:

asp.net mvc async await making main thread not blocking

  public async Task<ActionResult> Search(string q)
  {    
       var data = db.MediaPlanBilingInvoices.Where(m => m.IsDeleted == false);
            //allthe stuff        

            decimal? allinvoicetotal=0;
            decimal? allrototal = 0;
            if (Noofrecords > 0)
            {                
                    if (WebConstants.PrintMedia)
                    {
                       var roobject = data.Where(x => x.isPrint == true).SelectMany(m => m.MediaPlanBilingInvoiceDetails);
                       var roobjects =roobject.Select(m=>m.RoId);

                       Func<decimal?> functions = new Func<decimal?>(() => roobject.Sum(m => m.MediaPlanRO.MediaPlanROPrints.Sum(qq => qq.MediaPlanPrint.Amount)));
                       var tasksro = await System.Threading.Tasks.Task.Factory.StartNew<decimal?>(functions);    

                       allrototal = allrototal + tasksro.Result;

                }
                else if (WebConstants.ElectronicMedia)
                {
                    var roobject = data.Where(x => x.iselectronic == true).SelectMany(m => m.MediaPlanBilingInvoiceDetails);
                    var roobjects =roobject.Select(m=>m.RoId);

                    Func<decimal?> functions = new Func<decimal?>(() => roobject.Sum(m => m.MediaPlanRO.MediaPlanROPrints.Sum(qq => qq.MediaPlanPrint.Amount)));
                    var tasksro = await System.Threading.Tasks.Task.Factory.StartNew<decimal?>functions);   

                   allrototal = allrototal + tasksro ;
                }
              }                   
          }

                return Viewdata);
            }
        }

I am trying to calculate the sum of the ros in the different table for different criteria. 
The problem is that when the program reachers allrototal it stops and doesn't go to the next line until it bring down the result. I want to keep it running not stop there. how can i do it? 

A:

The core problem you're having is that async doesn't change the HTTP protocol (discussed in detail on my blog). With HTTP, you have one request and one response. If you return a response, then you can't also have something else running and then return another response later - HTTP just doesn't work that way.
So, on ASP.NET, async allows you to free up the thread but does not complete the response. The response is not sent until the async method is finished.
Furthermore, Task.Run is safer than StartNew, but neither of them should be used like this on ASP.NET because all it's doing is freeing up the request thread pool thread by using up another thread pool thread. So await Task.Run(() => functions()); is just a more expensive way of saying functions().
This method should just be made synchronous. There's no asynchronous work to do here. If you want your client to behave asynchronously, then your client will need to make its HTTP request asynchronously.

