หาสาเหตุไม่เจอ เมื่อcontent-type จาก application/json ถูกแทนที่ด้วย text/html เมื่อขึ้นserverค่ะ

Response.Headers.Add("Content-type", "text/json");
Response.Headers.Add("Content-type", "application/json");

function login() {
            alert("login");
            var myData = { userName: $('#username').val(), passWord: $('#password').val() };
            $.ajax({
                url: ('<%=Url.Action("Authenticate","Login")%>'),
                dataType: "json",
                contentType: "application/json;charset=utf-8",
                type: "POST",
                data: JSON.stringify(myData),
                success: function (dataReturn) {
                    alert("success");
                    window.location = '<%=Url.Action("Index","Home")%>'
                },
                error: function (dataReturn) {
                    alert("error");
                    $("#errorMes").html(dataReturn.MES).slideDown();
                }
            });
        }