Application setting is not saved

Question

I want to save a StringDictionary into the Application Settings in order to fill my listbox lbc_lastCustomersVisited with saved values at application launch.

Here is my application setting (XML format) :

<?xml version='1.0' encoding='utf-8'?>
<SettingsFile xmlns="http://schemas.microsoft.com/VisualStudio/2004/01/settings" CurrentProfile="(Default)" GeneratedClassNamespace="Wibe_EFI.Properties" GeneratedClassName="Settings">
    <Profiles />
    <Settings>
        <Setting Name="ApplicationSkinName" Type="System.String" Scope="User">
            <Value Profile="(Default)" />
        </Setting>
        <Setting Name="LastTimeWibeDataObtained" Type="System.String" Scope="User">
            <Value Profile="(Default)" />
        </Setting>
        <Setting Name="LastVisitedCustomer" Type="System.Collections.Specialized.StringDictionary" Scope="User">
            <Value Profile="(Default)" />
        </Setting>
  </Settings>

In my form, I got a StringDictionary local variable :

public partial class MainForm : XtraForm
{
    private StringDictionary lastVisitedCustomers = new StringDictionary();
    [...]
}

Here is how I fill my StringDictionary local variable :

private void btn_selectCustomer_Click(object sender, EventArgs e)
{
    DataRowView selectedRow = GetCustomersGridSelectedRow();
    lastVisitedCustomers.Add(GetCustomerID(selectedRow), String.Format("{0} - {1}", GetCustomerName(selectedRow), GetCustomerCity(selectedRow)));
}

(the StringDictionary is successfully filled)

At FormClosing, I save my setting :

private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
{
        Settings.Default["ApplicationSkinName"] = UserLookAndFeel.Default.SkinName;
        Settings.Default.LastVisitedCustomer = lastVisitedCustomers;
        Settings.Default.Save();
}

The setting ApplicationSkinName is successfully saved but not the lastVisitedCustomer StringDictionary. Because when I load my settings at application launch time, Settings.Default.LastVisitedCustomer is null.

Here is how I load my setting about the application skin (it works) :

public MainForm()
{
        InitializeComponent();
        InitSkinGallery();
        UserLookAndFeel.Default.SkinName = Settings.Default["ApplicationSkinName"].ToString();
}

But I cannot load my StringDictionnary right here because of a NullReferenceException.
So I load it here :

private void MainForm_Load(object sender, EventArgs e)
{
    _mySqlCeEngine = new MySqlCeEngine(this);
    ShowHomePanel();
    LoadLastVisitedCustomers();
}

private void LoadLastVisitedCustomers()
{
    if (Settings.Default.LastVisitedCustomer.Count > 0)
    {
        lastVisitedCustomers = Settings.Default.LastVisitedCustomer;
    }
    lbc_lastCustomersVisited.DataSource = new BindingSource(lastVisitedCustomers, null);
    lbc_lastCustomersVisited.DisplayMember = "Value";
    lbc_lastCustomersVisited.ValueMember = "Key";
}

But at this moment, Settings.Default.LastVisitedCustomer is null and I don't understand why. I tried some things like not using a local variable and read/write directly from Settings.Default.LastVisitedCustomer but I got the same problem.

Thanks,

Hellcat.

EDIT : Added full Settings.settings file (XML view)

Answer 1

I could not find any solution to store a Dictionary in the app settings so I decided to deal with a string and split it :

public partial class MainForm : XtraForm
{
    private Dictionary<string, string> lastVisitedCustomers;

    public MainForm()
    {
        InitializeComponent();
        InitSkinGallery();
        UserLookAndFeel.Default.SkinName = Settings.Default["ApplicationSkinName"].ToString();
        lastVisitedCustomers = StringToDictionary(Settings.Default["LastVisitedCustomer"].ToString());
    }

    private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
    {
        Settings.Default["ApplicationSkinName"] = UserLookAndFeel.Default.SkinName;
        Settings.Default["LastVisitedCustomer"] = DictionaryToString(lastVisitedCustomers);
        Settings.Default.Save();
    }

    #region Dictionary management

    private string DictionaryToString(Dictionary<string, string> dic)
    {
        if (dic.Count == 0)
        {
            return string.Empty;
        }
        else
        {
            string dicString = string.Empty;
            int i = 0;
            foreach (KeyValuePair<string, string> entry in dic)
            {
                if (i == 0)
                {
                    dicString = String.Format("{0} ## {1}", entry.Key, entry.Value);
                    i++;
                }
                else
                {
                    dicString += String.Format(" -- {0} ## {1}", entry.Key, entry.Value);
                }
            }
            return dicString;
        }
    }

    private Dictionary<string, string> StringToDictionary(string str)
    {
        Dictionary<string, string> dic = new Dictionary<string,string>();
        if (String.IsNullOrEmpty(str))
        {
            return dic;
        }
        else
        {
            string[] entries = Regex.Split(str, " -- ");

            foreach (string entry in entries)
            {
                string[] kvp = Regex.Split(entry, " ## ");
                dic.Add(kvp[0], kvp[1]);
            }

            return dic;
        }
    }
}
    #endregion

For now, it works.
I hope it will helps anyone in my situation.

Notice : You may have to modify my dictionary methods in order to handle every cases for Exceptions. But I think this is okay now.

Sorry for any english mistakes

Answer 2

If you want to try, I tried to produce the error you get by creating a new formapplication:

namespace WindowsFormsApplication2
{
  public partial class Form1 : Form
  {

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        test.Text = (string)Settings.Default["lastCustomers"];
    }

    private void Form1_FormClosed(object sender, FormClosedEventArgs e)
    {
        Settings.Default["lastCustomers"] = test.Text;
        Settings.Default.Save();
    }
  }
}

In this example the code works. Just create a new Form-Application and add a textbox into it with the name test. Every time you close the program and restart it, the string you wrote into the textbox will be saved and reloaded into test.Text.

Specifically in your case your constructor should then look like this: (Possible solution)

public MainForm()
{
    InitializeComponent();
    InitSkinGallery();
    UserLookAndFeel.Default.SkinName = Settings.Default["ApplicationSkinName"].ToString();
    lastVisitedCustomers = (StringDictionary)Settings.Default["LastVisitedCustomer"];
}

Afterwards you save the settings the same way you loaded them:

private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
{
    Settings.Default["ApplicationSkinName"] = UserLookAndFeel.Default.SkinName;
    Settings.Default["LastVisitedCustomer"] = lastVisitedCustomers;
    Settings.Default.Save();
}

This should solve your problem!

EDIT Oh and of course, your loading functions looks different then:

private void MainForm_Load(object sender, EventArgs e)
{
    _mySqlCeEngine = new MySqlCeEngine(this);
    ShowHomePanel();
    LoadLastVisitedCustomers();
}


private void LoadLastVisitedCustomers()
{
    lbc_lastCustomersVisited.DataSource = new BindingSource(lastVisitedCustomers, null);
    lbc_lastCustomersVisited.DisplayMember = "Value";
    lbc_lastCustomersVisited.ValueMember = "Key";
}