How to access listbox items in asp.net code behind which i added through jqurey

I'm working on a project and presently I'm doing a module that belongs to a posting article page. In this page we have a option to add keywords by using textbox and button.

I done this by using jquery to add textbox enter keyword to listbox successfully.

If a user wants to remove any specific keyword after adding it the to listbox the user can remove it by selecting that keyword in the listbox then a remove button appears. If the user click that remove button keyword removed from listbox.

Problem :

After adding keyword successfully to listbox by using jquery but i can't access that listbox items in C# Code behind

Asp.net Page Listbox:

<a id="arkyw" href="#/"><font color="#cc0000">Remove Keyword</font></a>
<span id="spKeyword" style="color:#e74c3c;"></span>    
<asp:ListBox ID="listBoxKeywords" runat="server" CssClass="list-group" style="border:0px; overflow-y:hidden; height:83px; width:300px;">

JQuery :

var count = [];
    var i = 0;
    $("#btnAddKeyword").click(function () {        
        var txt = $("#txtkeyword").val();
        $('[id$=listBoxKeywords]').show();
        if (jQuery.inArray(txt, count) != "-1") {
            $("#spKeyword").text('Keyword alread exists');
        } else {
            var listCount = $('[id$=listBoxKeywords] option').length;
            if (listCount <= 4) {
                count[listCount] = txt;
                var alreadyExist = false;
                $('[id$=listBoxKeywords] option').each(function () {
                    if ($(this).val() == txt) {
                        $("#spKeyword").text('Keyword alread exists');
                        alreadyExist = true;
                        return;
                    }
                });
                if (!alreadyExist) {
                    $('[id$=listBoxKeywords]').append($('<option></option>').attr('value', count[listCount]).text(txt));
                }
            } else {
                $("#spKeyword").text('5 Keyword limit exceed');
            }
        }
    });
    //Remove Value from the List
    $('[id$=listBoxKeywords]').click(function (e) {        
        var $target = $(e.target);
        if ($target.is('option')) {
            $("#arkyw").show();            
        }
    });
    $("#arkyw").click(function () {
        var a = $('[id$=listBoxKeywords] option:selected').val();
        var id = $('[id$=listBoxKeywords] option').length;
        //alert('ListCount : ' + a);
        //alert('Total List Item : ' + id);
        //alert('After Remove : ' + count[a-1]);
        count = jQuery.grep(count, function (e) {
            $('[id$=listBoxKeywords] option:selected').remove();
            return e != a;

        });        
    });

how to access listbox items in C# Code behind