返回arraylist时无法显示wcf rest页面

Question

我正在制作WCF REST服务 当我回到一个arraylist。 enter image description here我无法显示该页面 为什么会这样？

这是我在restservice.svc的代码：

public ArrayList getmenu()
    {
        SqlConnection conn;
        string konek = "Data Source=DESKTOP-DUB3J4D;Initial Catalog=Restoran;Integrated Security=True";
        conn = new SqlConnection();
        try
        {
            conn.ConnectionString = konek;
            conn.Open();
            ArrayList userArray = new ArrayList();
            SqlDataReader reader = null;
            string query = "select Id_Menu as 'ID', Nama_Menu as 'Nama Menu' ,  Harga_Menu as 'Harga Menu', Path_Gambar as'Gambar', tanggal_input as 'Tanggal Input'  from Menu";
            SqlCommand cmd = new SqlCommand(query, conn);
            reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                menu datamenu = new menu();
                datamenu.nama = reader.GetString(1);
                datamenu.harga = reader.GetInt32(2);
                datamenu.pathimg = reader.GetString(3);
                string tanggal =Convert.ToString(reader.GetDateTime(4));
                datamenu.date = tanggal;
                userArray.Add(datamenu);
            }
            return userArray;
        }
        catch (SqlException ex)
        {
            throw ex;
        }
        finally
        {
            conn.Close();
        }



    }

这是我的操作合同

  [OperationContract]
    [WebInvoke(Method = "GET",
                UriTemplate = "/getmenu"
              , RequestFormat = WebMessageFormat.Json
               , ResponseFormat = WebMessageFormat.Json)]
 ArrayList getmenu();