How to use comma-delimited syntax in the jquery ajax method

I find i can not pass comma-delimited parameters to the server mothod if i use the code below, the data is
{ Ids:“7,8,9” }, the server return RequestBindingException, the method is put

            headers: {
                Accept: "application/json; charset=utf-8",
                "Content-Type": "application/json; charset=utf-8"
            //async: false,
            url: urlParam,
            type: "PUT",
            data: dataParam,
            cache: true,
            Accept: "text/json;"

remove “Content-Type”: “application/json; charset=utf-8”
all works.