Maintain page index in gridview after a PostBack

I'm occupying a gridview format which is applied with the following function, this includes a search block, a filtering by number of records but the problem is that when the number of records exceeds the limit and this stops to have more of a page, by selecting a radiobutton that is in a templatefield in the first column this has the property of AutoPostback so when reloading the table returns to the first page of the gridview, I would like to know how to rescue the index of the current page of the gridview, I already tried with the pageindexchanging function, When inquiring with "chrome inspection" I realized that the only property that changes is data-dt-idx, in case if someone has taken this format and can help me with this problem, I program in Visual Studio 2010 in C # asp .net

$(document).ready(function () {
                $("#MainContent_gvListado").gridviewFix().DataTable({
                    language: { "url": "//cdn.datatables.net/plug-ins/9dcbecd42ad/i18n/Spanish.json" },
                    scrollX: true
                });
            });