title: An asynchronous operation cannot be started at this time Exception occurs on calling WebService?
body: <p>In my ASP.NET MVC 3 project I'm calling a web service for login authentication. But it throws an exception:</p>
  
  <p><img src="https://i.stack.imgur.com/cFDbB.jpg" alt="Asynchronous Exception"></p>
  
  <p>Exception Details:</p>
  
  <blockquote>
    <p>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 &lt;%@ Page Async="true" %>.</p>
  </blockquote>
  
  <p>How to fix this issue?</p>