ASP.NET MVC 5 – Form Post Cross Domain Validation

ASP.NET MVC 5 – Form Post Cross Domain Validation

@using( Html.BeginForm() )    {       @Html.AntiForgeryToken();       … …       … …       <input type="Submit" value="Submit" />    }

[HttpPost]    [ValidateAntiForgeryToken]    public ActionResult Index(… …)    {       return View();    }

Web Form HTML Code from Client Side …

< form action="… …" method="POST" >       < input name="__RequestVerificationToken" type="hidden"          value="_bqy-L0mG7K4n5hCwcOJ1ANuw0Lm5jydnyS8D6GPQKsRaIxjS74tRT6kqE4QZlXNXIiC7NrOn4lJVvfsbvGwf79U" />       < input type="Submit" value="Submit" />    < /form >

Remarks :
 
If the "__RequestVerificationToken" Token is not existed from the Web Form,
the Web Application Controller cannot get the RequestVerificationToken for Validation.
Then the Form Post Submission Error "The required anti-forgery form field "__RequestVerificationToken" is not present." would be thrown …
 
The Reason is as follow :
 
i) The Web Form Client is submitted from Untrusted Website.
   The Form Post Application Server and Web Form Client is not in the same Domain Name ( CORS ).
   Then there is no "__RequestVerificationToken" Element which is Posted the Web Form …
 
ii) The Developer has not added the AntiForgeryToken HTML Helper Control in the form.