Post form data to Controller's action with Ajax

I'd recommend just writing your own AJAX calls with jQuery. It's more flexible than MVC's helpers anyway

@Html.ActionLink("Share", "Share", new { }, new { id = "share" })

And then a function

$("#share").click(function (e) {
   e.preventDefault();
   //Show loading display here
   var form= $("#shareForm");
   $.ajax({
       url : '@Url.Action("Share")',
       data: form.serialize(),
       type: 'POST',
       success: function(data){
          //Show popup
          $("#popup").html(data);
       }
   });
});