Null value multiselect dropdown in MVC

See more:

Ajax

jQuery

C#3.5

MVC5

Hi All,
IN MVC i have a multiselect dropdown list on change i am populating another dropdown. But not able to get multiselect values on the controller below is my code.

View
--------------

@Html.DropDownList("Country", ViewData["country"] as List<SelectListItem>, new {@multiple="multiple", style = "width:250px", @class = "dropdown1" })

Ajax call

<script type="text/javascript">
    $(document).ready(function () {
       
        $("#Country").change(function () {
            
            var abc = $("#Country").val();
            alert(abc);
           

            $("#State").empty();
            $.ajax({               
                type: 'POST',
                url: '@Url.Action("GetStates")', // we are calling json method
                dataType: 'json',
                //data: { id: $("#Country").val() },
                data: { "CountryId": abc },
                cache: false,
                success: function (states) {
                    // states contains the JSON formatted list
                    // of states passed from the controller
                    $.each(states, function (i, state) {

                        alert(state.Value);
                        $("#State").append('<option value="' + state.Value + '">' + state.Text + '</option>');
                    }); // here we are adding option for States
                },
                error: function (ex) {
                    alert('Failed to retrieve states.' + ex);
                }
            });
            return false;
        })
    });
</script>

Controller
-------------------------

public JsonResult GetStates(string CountryId)
       {
          return null;
}

But i am getting CountryId as NULL for multi select dropdown case only for normal dropdown i am getting the value,

Please help

What I have tried:

i have tried the above code for the same but always get a null value for multiselect dropdown case