ajax在后台怎么获取data值？

JScript code

options = {                    type: "POST",                    url: ajaxPage,                    data:{"Formula":escape(textarea),"FieldNames":escape(fieldNames)},                    contentType: "application/json;charset=utf-8",                    dataType: "string",                    async: false                };                returnText = $.ajax(options).responseText;

后台onLoad事件

C# code

if (Request["mn"] != null && Request["mn"] == "Detection")                {                    Response.ContentType = "application/json";                    Response.Write(IsExist());                    Response.End();                }

在if里面怎么获取data的值？

[解决办法]
取消escape，jq已经自动用encodeURIComponent编码过一次了

JScript code

options = {                    type: "POST",                    url: ajaxPage,                    data:{"Formula":textarea,"FieldNames":fieldNames},///////////                   // contentType: "application/json;charset=utf-8",//不要设置contentType为这个，要不服务器端生成不了键值对                    //dataType: "string",//dataType没有string类型，不过设置为这个也行，会自动变为text                    dataType: "text",                    async: false                };