How do you correctly store a custom object in isolated storage using C#?

Question

Working on a sideproject with WP8, but having trouble getting IsolatedStorage working. I have looked at dozens of posts seemingly asking the same question, but I haven't been able to get any of the solutions to work. The application is a simple task organizer where I have created my own Task Objects, one being a Summary Task and each SummaryTask containing a list of BasicTasks. I have tried using XMLSerializing only to run into problems because I was using an ObservableCollection. Thought I could change the collection to a Subclass of INotifyPropertyChanged but that didn't work either. Quite frankly, I'm still getting the hang of the different between the two anyways. So anyways, my latest attempt involves trying to use IsolatedStorage Settings and that didn't work either. Here is my class definition:

class SummaryTask : TaskItem
{
    public List<BasicTask> children = new List<BasicTask>();
    private string sumTaskName;
    private int sumTaskId;
    public SummaryTask()
    {

    }
    public SummaryTask(string name, int id)
    {
        sumTaskName = name;
        sumTaskId = id;
    }
    public string SumTaskName
    {
        get { return sumTaskName; }
        set { sumTaskName = value; }
    }
    public int SumTaskId
    {
        get { return sumTaskId; }
        set { sumTaskId = value; }
    }
    public void addTask(string taskName, string taskText, int taskId){
        children.Add(new BasicTask(taskName, taskText, taskId));
    }
    public List<BasicTask> CHILDREN
    {
        get { return children; }
    }
}
}

I create a list of this SummaryTask in a Global variable and use it throughout my pages for easy access. Here is what the beginning of my MainPage.xaml.cs file looks UPDATED:

    public MainPage()
    {
        InitializeComponent();
        BackKeyPress += OnBackKeyPressed;
        if (Global.settings.Contains("list"))
        {
            Global.list = (List<SummaryTask>)Global.settings["list"];
        }
        else
        {
            Global.list = new List<SummaryTask>();
        }
    }

Guidance on the poor quality of my code and how to improve it is also accepted. Thank you.

Edit: The exception indicates that an item with the same key has already been created. The stacktrace doesn't show anything of importance in this case. I should also note that the exception is thrown after adding an object to the list and trying to save it, not while compiling.

The piece of code I am using to try to save to the Isolated Storage is here, it triggers when I navigate to MainPage.xaml:

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
    {
        resultList.SelectedItem = null;
        Global.settings["list"] = Global.list;
        Global.settings.Save();
    }

No exceptions anymore, but exiting the app and reentering isn't pulling up any saved data.

When you ask a question involving an exception, please give details of the exception. What's the message? Anything interesting in the stack trace? — Jon Skeet
My apologies, I have added information related to the Exception. Seems I am trying to create the same IsolatedStorage entry twice. I can see how it's happening, but I don't know how I'd save it without using add. settings.Save() brings up a security exception.. — Wilcoholic
Details on that security exception: it tells me adding a public parameterless constructor will solve the issue, but I'm not sure where it wants me to add it..I already have it in my SummaryTask class as seen above. — Wilcoholic

Jon Skeet Jon Skeet · Accepted Answer · 2012-12-01T10:46:08

The problem with Add is very simple to fix - just use the indexer instead, which allows you to overwrite an entry with the same name:

settings["list"] = Global.list;

That won't fix the Save call... but you'd need to give more details about what exception (not just "it tells me", the full exception details) to help us help you more.

How do you correctly store a custom object in isolated storage using C#?

1 Answers