Question

I’ve a windows forms desktop application which keeps contact details. The application stores contacts data as below when closing the application,

private void MyForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            try
            {
                Properties.Settings.Default.ApplicationData = mydata;
                Properties.Settings.Default.Save();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

When application starts it load data as below,

      try
      {     
         this.mydata = (DataHandeler) Properties.Settings.Default.ApplicationData;

}
        catch (NullReferenceException)
        {
            mydata = new DataHandeler();
        }
        catch (Exception e)
        {
            MessageBox.Show(e.Message);
            mydata = new DataHandeler();
        }

SettingsSerializeAs has been added into Settings.Designer.cs as below,

[global::System.Configuration.UserScopedSettingAttribute()]
[global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
[global::System.Configuration.SettingsSerializeAs( System.Configuration.SettingsSerializeAs.Binary)]

public object ApplicationData {
    get {
        return ((object)(this["ApplicationData"]));
    }
    set {
        this["ApplicationData"] = value;
    }

But application cannot recover already stored data after each time I close and re-open the application. Nullreferenceexception is thrown when application trying to load data. How can I recover the data?

Answer 1

Is there an exception being thrown when the settings are saved or loaded?

Are the settings actually being saved to the file?
On Windows Vista or 7, there should be a user.config file in a directory named something like:

C:\Users\{user_name}\AppData\Roaming\Microsoft\{project_or_assembly_name}\{version_number}\user.config

Is your DataHandeler class serializable?

This MSDN thread might also help.