ASP.NET MVC 5和WCF异步故障

Question

Our application uses WCF as data provider and on some pages we have a multiple calls to different services. Good piece to optimize I thought, and started to rewrite it to the async . So before the rewrite it looks like

public ActionResult SomeAction(int id)
{
var r1 = AService.Call1();
var r2 = BService.Call2();
var r3 = CService.Call3();
//another logic
}

and now it turned to

public async Task<ActionResult> SomeAction(int id)
{
var r1 = await AService.Call1Async();
var r2 = await BService.Call2Async();
var r3 = await CService.Call3Async();
//another logic
}

With this approach I faced two problems:

1. After first service call application falls into unending loading and no other actions performed. Debugging show the same — first call and nothing after that.
2. Some of our classes won't work with async methods, ae our static AuthorizationProvider.

Update: @zuckerberg answer helps with optimization (I'm creating tasks and putting them in awaitable Task.WhenAll() ), but I'm still getting hangs on WCF services — while synchronous calls going correctly, asynchronous calls turning calling logic to sleep and never awakes it back.

Answer 1

with async/await they run asynchronously. Which means they don't wait for each other or the main thread. If there are dependancies or you need to wait for all 3 to finish first before returning a result, then I suggest using something like:

var r1 = await AService.Call1Async();
var r2 = await BService.Call2Async();
var r3 = await CService.Call3Async();

await Task.WhenAll(r1, r2, r3);
//more logic

Hope this helps nudge you in the right direction. However, without seeing more code, I can't tell if by just async/await'ing your calls will actually improve performance or not (it's not always a performance booster) and your time/effort might be better spent elsewhere.

Good luck!

Answer 2

1.Starting functions with inner async calls from constructor of static class is a bad idea, but SomeMethodAsync().Result helps — of course there's no benefit for controller, but in that little case it acceptable.

2.Yes, I misunderstood async/await , so I rewrite code to something like this:

var get1Task = AService.Call1Async();
var get2Task = BService.Call2Async();
var get3Task = CService.Call3Async();

await Task.WhenAll(get1Task, get2Task, get3Task);
var r1 = get1Task.Result;
var r2 = get2Task.Result;
var r3 = get3Task.Result;
//more logic

It gave me a good speedup on pages with lot of WCF calls and I'm kinda happy.

My thanks going to @zuckerberg for pointing to the right direction.