Hi trex0911,

Refer the below link.

Disable Update button when reordering is not modified in GridView using jQuery Drag and Drop in ASP.Net

If you want disable the button then use the below script.

<script>
    $(function () {
        $('[id*=btnUpdate]').attr("disabled", true);
        $("[id*=gvLocations]").sortable({
            items: 'tr:not(tr:first-child)',
            cursor: 'pointer',
            axis: 'y',
            dropOnEmpty: false,
            start: function (e, ui) {
                ui.item.addClass("selected");
            },
            stop: function (e, ui) {
                ui.item.removeClass("selected");
                $('[id*=btnUpdate]').attr("disabled", false);
            },
            receive: function (e, ui) {
                $(this).find("tbody").append(ui.item);
            }
        });
    });
</script>

If you want to hide the button initially then use the below script.

<script type="text/javascript">
    $(function () {
        $('#btnUpdate').hide();
        $("[id*=gvLocations]").sortable({
            items: 'tr:not(tr:first-child)',
            cursor: 'pointer',
            axis: 'y',
            dropOnEmpty: false,
            start: function (e, ui) {
                ui.item.addClass("selected");
            },
            stop: function (e, ui) {
                ui.item.removeClass("selected");
                $('#btnUpdate').show();
            },
            receive: function (e, ui) {
                $(this).find("tbody").append(ui.item);
            }
        });
    });
</script>