独立存储-如何读取附加数据

我有一个Game application(WP8)，我们在其中保存多个攻击的分数并将其显示给用户。

我有一个字段为noOfStonesPicked和noOfFruitsPicked的对象。

这是我的代码：

MyTopic topicObj = new MyTopic ();
for (int i = 0; i <= 2; i++)
            {
                Test mt = new Test();
                mt.noOfStonesPicked = 12;
                mt.noOfFruitsPicked= 20;
                topicObj.Stats.Add(mt);
                }                
WritetestTopicState(topicObj);

现在3次尝试，每次都有noOfStonesPicked -12 and noOfFruitsPicked - 20

现在我保存这样：

public static void WritetestTopicState(MyTopic topic)
        {
            try
            {
                using (var store = IsolatedStorageFile.GetUserStoreForApplication())
                {
                    using (StreamWriter sw = new StreamWriter(store.OpenFile("12.xml", FileMode.Append, FileAccess.Write)))
                    {
                        XmlSerializer serializer = new XmlSerializer(typeof(MyTopic));
                        serializer.Serialize(sw, topic);
                        serializer = null;
                    }
                }
            }
            catch (Exception)
            {
                throw;
            }
        }

现在我如何检索这些值并显示？

编辑

这就是我尝试过的：

public static MyTopic ReadMockTestTopicState()
        {
            MyTopic topic = null;
            try
            {
                using (IsolatedStorageFile isoStore = IsolatedStorageFile.GetUserStoreForApplication())
                {
                    // Read application settings. 
                    if (isoStore.FileExists("11.xml"))
                    {
                        using (var store = IsolatedStorageFile.GetUserStoreForApplication())
                        {
                            using (StreamReader SR = new StreamReader(store.OpenFile("12.xml", FileMode.Open, FileAccess.Read)))
                            {
                                XmlSerializer serializer = new XmlSerializer(typeof(MyTopic));
                                topic = (MyTopic)serializer.Deserialize(SR);
                                serializer = null;
                            }
                        }
                    }
                    else
                    {
                        // If setting does not exists return default setting.
                        topic = new MyTopic();
                    }
                }
            }
            catch (Exception)
            {
                throw;
            }
            return topic;
        }

XmlSerializer serializer = new XmlSerializer(typeof(MyTopic));
StreamReader reader = new StreamReader(path);
_myTopic = (MyTopic)serializer.Deserialize(reader);
reader.Close();