此时无法启动异步操作 调用 WebService 时发生异常？

Question

In my ASP.NET MVC 3 project I'm calling a web service for login authentication. But it throws an exception:

Exception Details:

An asynchronous operation cannot be started at this time. Asynchronous operations may only be started within an asynchronous handler or module or during certain events in the Page lifecycle. If this exception occurred while executing a Page, ensure that the Page is marked <%@ Page Async="true" %>.

How to fix this issue?

Answer 1

Make sure that your Controller method returns an async Task.

public class ServiceController : Controller 
{
    public async Task<ActionResult> Index()
    {       
        var service = new Service();
        await service.CallMethodAsync();    
        return View();
    }
}

Basically, the documentation is written in a way where they believe you are only using ASP.NET WebForms, however obviously you can use this in MVC applications too, so their documentation needs to be updated.

Answer 2

您正在调用 ASYNC 方法，因此您必须在页面声明 <%@ Page .....%> 中添加 Async="true"。