@using (Ajax.BeginForm("Login", new AjaxOptions { HttpMethod = "POST", UpdateTargetId = "Login",InsertionMode = InsertionMode.Replace, OnSuccess = "Success", OnFailure = "onError" }))
 {

 }

[httpPost]
public ViewResult Login(LoginModel model)
{
   if (ModelState.IsValid)
   {

   }
   else
   {
     ModelState.AddModelError("login is fail")
   }
   return View("Login",model)
}

[HttpPost]
public ActionResult Login(LoginModel model)
{
    if (ModelState.IsValid)
    {
        // everything went fine and we want to redirect in this case =>
        // we pass the url we want to redirect to as a JSON object:
        return Json(new { redirectTo = Url.Action("SomeController", "SomeAction") });
    }
    else
    {
        // there was an error => add an error message
        ModelState.AddModelError("login is fail")
    }

    // return a partial view instead of a full vire
    return PartialView("Login",model)
}

@using (Ajax.BeginForm("Login", new AjaxOptions { HttpMethod = "POST", OnSuccess = "loginAjaxSuccess" }))
{

}

function loginAjaxSuccess(result) {
    if (result.redirectTo) {
        // the controller action returned a JSON result => it was a successful login
        // => we redirect the browser to this url
        window.location.href = result.redirectTo;
    } else {
        // the action returned a partial view with the form containing the errors
        // => we need to update the DOM:
        $('#Login').html(result);
    }
}

} else {
    // the action returned a partial view with the form containing the errors
    // => we need to update the DOM
    $('#Login').html(result);

    // Now that the DOM is updated let's refresh the unobtrusive validation rules on the form:
    $('form').removeData('validator');
    $('form').removeData('unobtrusiveValidation');
    $.validator.unobtrusive.parse('form');
}