find checked radio button throug jQuery

$("#_chkbox").change(function () {
            var items = $(".childCheckBox").find("input");
            if ($('#_chkbox').is(':checked') == false) {
                for (i = 0; i < items.length; i++) {
                    if (items[i].type == "checkbox") {
                        items[i].checked = false;
                    }
                }
            }
            if ($('#_chkbox').is(':checked') == true) {
                for (i = 0; i < items.length; i++) {
                    if (items[i].type == "checkbox") {
                        items[i].checked = true;
                    }
                }
            }
        });

Generate CSV File in ASP.Net

 Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click

        Response.Clear()

        Response.ContentType = "text/csv"

        Response.AppendHeader("Content-Disposition", String.Format("attachment; filename={0}.csv", DateTime.Now))

        Dim _web As SPWeb = New SPSite(SPContext.Current.Site.Url).OpenWeb()

        Dim _list As SPList = _web.Lists("List Name")

        Dim _items As SPListItemCollection = _list.Items

        For Each _item As SPListItem In _items

            Response.Write(_item("Title") + "," + CStr(_item("ID")) + "," + System.Environment.NewLine)

        Next

        Context.Response.End()

    End Sub