function D() {                var cks = document.getElementsByTagName("input");                var a = new Array();                for (var i = 0; i < cks.length; i++) {                    if (cks[i].type == "checkbox" && cks[i].checked) {                        a.unshift(cks[i].title);                    }                }               $.ajax({                    type: "get",                    dataType: "text",                    url: "../controller/Delete_message.ashx",                    data: {"MeeageId":a},                    beforeSend: function() { $("#HeadDiv").text("Send...").show("slow") },                    complete: function() { $("#HeadDiv").text("Send end...").hide("slow"); },                    success: function(msg) {                        alert(msg);                    }                })       }后臺代碼：       context.Response.Write( context.Request.Params["MessageId"])  這樣獲取是空值  怎么辦哦？