IIS 8.5服务器2012不返回json

Question

在使用IIS Express的localhost上，当我将其复制到服务器2012上的IIS 8.5时，不会给我任何错误，当我请求json结果时，总是给出“内部服务器错误500”。

这是代码。

控制器

        [HttpGet]
    public JsonResult TicketsAbertos(string username)
    {

        Computer computer = new Computer();
        computer.GetHostDetails();


        //return Json(JsonConvert.SerializeObject(result), JsonRequestBehavior.AllowGet);
        string json = JsonConvert.SerializeObject(computer.GetOpenTickets(computer.User));
        return Json(json, JsonRequestBehavior.AllowGet);

       // return this.Json(computer.GetOpenTickets(computer.User), JsonRequestBehavior.AllowGet);
    }

模型

public List<Computer> GetOpenTickets(string user_)
    {

        List<Computer> listar = new List<Computer>();
        Dictionary<string, string> list = new Dictionary<string, string>();
        //int result;
        string connetionString = null;
        SqlConnection cnn ;
        connetionString = "Data Source=.\\HELPDESK;Initial Catalog=" + db + ";User ID=" + user_db + ";Password=" + pwd + "";
        cnn = new SqlConnection(connetionString);
        try
        {
            cnn.Open();
            string query = "SELECT * FROM [tbl_user_details] JOIN [tbl_assistance_description] ON [tbl_user_details].username LIKE @user_ AND [tbl_assistance_description].Status LIKE @status_ ORDER BY [tbl_assistance_description].Date DESC";
            try
            {
                SqlCommand command = new SqlCommand(query, cnn);
                command.Parameters.AddWithValue("@status_", "Aberto");
                command.Parameters.AddWithValue("@user_", user_);
                try
                {
                    SqlDataReader dataReader = command.ExecuteReader();
                    if (dataReader.HasRows)
                    {
                        while (dataReader.Read())
                        {
                            try 
                            {

                                listar.Add(new Computer()
                                {
                                    //ID = dataReader.IsDBNull(0) ? Convert.ToInt32(null) : dataReader.GetInt32(0),
                                    User = dataReader.IsDBNull(1) ? null : dataReader.GetString(1),
                                    Host = dataReader.IsDBNull(2) ? null : dataReader.GetString(2),
                                    IP = dataReader.IsDBNull(3) ? null : dataReader.GetString(3),
                                    Location = dataReader.IsDBNull(4) ? null : dataReader.GetString(4),
                                    ID = dataReader.IsDBNull(6) ? 0 : dataReader.GetInt32(6),
                                    Report = dataReader.IsDBNull(7) ? null : dataReader.GetString(7),
                                    Description = dataReader.IsDBNull(8) ? null : dataReader.GetString(8),
                                    Date = dataReader.GetDateTime(10).ToString(),
                                    Status = dataReader.IsDBNull(11) ? null : dataReader.GetString(11)
                                });

                            }
                            catch (SqlException ex)
                            {
                                listar.Add(new Computer()
                                {
                                DB_RESULT = ex.Message
                                });
                            }
                        }
                    }
                }
                catch (SqlException ex)
                {
                    listar.Add(new Computer()
                    {
                        DB_RESULT = ex.Message
                    });
                }
                cnn.Close();
            }
            catch (SqlException ex)
            {
                listar.Add(new Computer()
                {
                    DB_RESULT = ex.Message
                });
            }
        }

        catch (SqlException ex)
        {
            listar.Add(new Computer()
            {
                DB_RESULT = ex.Message
            });
        }
        return listar;


    }

Ajax请求

 $("#Aticketsabertos").live("click", function (evt) {
    $(".featured .content-wrapper").slideUp();
    $("#AdminMenu").hide();
    var result = "";
    $("#result").fadeOut();
    evt.preventDefault();

    $("#indexform").hide();
    $("#Ticketsabertos").show();
    $("#Ticketsfechados").hide();
    $(".featured .content-wrapper").slideDown();
    $.ajax({
        type: "GET",
        url: "helpdesk/Home/TicketsAbertos",
        //data: { username: $("#User").val() },
        //jsonp: false,
        dataType: "json",
        contentType: "application/json",
        success: function (output) {
            output = JSON.parse(output);
            $("#result").show();
            console.log(output);
            $.each(output, function (i, item) {
                    if (item.DB_RESULT != "") {
                        result += item.DB_RESULT;
                    } else {
                        result += "<tr>" +
                            //"<th>User</th><td>" + item.User + "</td>" +
                            //"<th>Host</th><td>" + item.Host + "</td>" +
                            //"<th>IP</th><td>" + item.IP + "</td>" +
                            "<td>" + item.ID + "</td>" +
                            "<td>" + item.Report + "</td>"+
                            "<td>" + item.Description + "</td>" +
                            "<td>" + item.Location + "</td>" +
                            "<td>" + item.Date + "</td>" +
                            "<td class='statusaberto'>" + item.Status + "</td>" +
                            "</tr>"
                        ;
                    };
            }),
                $("#result").removeClass().addClass("result_table").fadeIn().html("<table><tr>"+
                    "<th>ID</th><th>Tipo</th><th>Descrição</th><th>Local</th><th>Data</th><th>Status</th>" + result + "<table>");

        },
        error: function (xhr, textStatus, jqXHR) { 
            $("#result").fadeIn();
            $("#result").removeClass().addClass("result_error").text("ERRO:" + xhr.status + " " + xhr.statusText + " " + DisplayError(xhr));
            console.log(DisplayError(xhr));
        }
     });
    return false;
});

响应标题始终是“text / html”，而不是json。 mime类型.json它被添加。