problem Storing a list of Objects in Isolated Stor

问题:

I am trying to store a list of objects I created in the isolated storage and be able to display them in a list by auto generating a title for them. So far the code works but once I tombstone the app and start it up all my data is saved except for the list of objects. I think my problem may be with how I initialize the list in the first place, or possibly how I am displaying the names. Any help is appreciated.

this code is in my App.xaml.cs:

public partial class App : Application
    {
      public List<my_type> testList = new List<my_type>();

        void loadvalues()
        {
         IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;
         List<my_Type> L;
         if (settings.TryGetValue<List<DrinkSesh>>("Storage", out L))
         { testList = L; }
        }

        void savevalues()
        {
        IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;
        settings["Storage"] = testList;
        settings.Save();
        }
     }

This code is on my mainPage to add the items to the list:

(Application.Current as App).testList.Add(new my_type());

and this code is to implement the titles onto the screen on a different page:

 public different_class()
{
        {
                InitializeComponent();
                for (i = 0; i < (Application.Current as App).testList.Count; i++)
                {
                    CreateATextBlock((Application.Current as    App).testList[i].Title_ToString(), i);
                }
        }

        private void CreateATextBlock(String title,int num)
        {
            testblockname = new TextBlock();
            testblockname.Text = (num + 1) + ". " + title;
            DrList.Children.Add(testblockname);
        }
}

Thank you in advance!

回答1:

Here is the code I use to save and load lists of objects from isolated storage.

public class IsoStoreHelper
{
    private static IsolatedStorageFile _isoStore;
    public static IsolatedStorageFile IsoStore 
    { 
        get { return _isoStore ?? (_isoStore = IsolatedStorageFile.GetUserStoreForApplication()); }
    }

    public static void SaveList<T>(string folderName, string dataName, ObservableCollection<T> dataList) where T : class
    {
        if (!IsoStore.DirectoryExists(folderName))
        {
            IsoStore.CreateDirectory(folderName);
        }

        string fileStreamName = string.Format("{0}\\{1}.dat", folderName, dataName);

        using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream(fileStreamName, FileMode.Create, IsoStore))
        {
            DataContractSerializer dcs = new DataContractSerializer(typeof(ObservableCollection<T>));
            dcs.WriteObject(stream, dataList);
        }
    }

    public static ObservableCollection<T> LoadList<T>(string folderName, string dataName) where T : class
    {
        ObservableCollection<T> retval = new ObservableCollection<T>();

        if (!IsoStore.DirectoryExists(folderName))
        {
            IsoStore.CreateDirectory(folderName);
        }

        string fileStreamName = string.Format("{0}\\{1}.dat", folderName, dataName);

        using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream(fileStreamName, FileMode.OpenOrCreate, IsoStore))
        {
            if (stream.Length > 0)
            {
                DataContractSerializer dcs = new DataContractSerializer(typeof(ObservableCollection<T>));
                retval = dcs.ReadObject(stream) as ObservableCollection<T>;
            }
        }

        return retval;
    }
}

回答2:

By simply adding your collection (List) to your IsolatedStorageSettings you are relying on the built in serializer (the DataContractSerializer) to serialize your object for persisting to disk.

Are you sure your object can be correctly serialized and deserialized?

Doing this yourself is probably the easiest way to do this.

If you do this yourself, not that: - DataContractSerializer is slow - DataContractJsonSerializer is faster - Json.net is faster still - Binary serialization is fastest.

When serializing yourself you should also save in an IsolatedStorageFile rahter than in the settings. This can help with performance and also adds flexibility which can aid debugging and testing.