从 Web API 同步调用外部 api

Question

I need to call an external api from my Web API 2 controller, similar to the requirement here:

Calling external HTTP service using HttpClient from a Web API Action

However, the solution above requires adding the async keyword to my api method's GET call, thus making my call asynchronous. I prefer to present clients of my API with a synchronous method but still be able to call the external api from my own (and will need that to return before my api returns). Is there a way to do this?

Answer 1

Blocking on an async operation could be dangerous. It hurts performance and could lead to deadlocks (more in Should I expose synchronous wrappers for asynchronous methods? )

But if you're sure that's what you want to do, It's better IMO to use GetAwaiter().GetResult() :

using (HttpClient httpClient = new HttpClient())
{
    var response = httpClient.GetAsync(_endpoint).GetAwaiter().GetResult();
    var result = response.Content.ReadAsStringAsync().GetAwaiter().GetResult();
    // Do stuff...
}

It's the same whether it's a Task or Task<T> , it's the same call await translates to (although with await the task already completed) and Task.Result (or Task.Wait ) wraps any exceptions in AggregateException while GetAwaiter().GetResult() throws only the first Exception as await does.