Question

I’m trying to move some of the code behind in my project to a separate class. The part that I am interested in moving is the GetData method. I would like to move it out of my code behind to a separate class called DataAccess. I would appreciate your assistance. Thanks!

MainWindow.xaml.cs

namespace Contact_Interests
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    private ObservableCollection<AggregatedLabel> myAggLabels;

    public ObservableCollection<AggregatedLabel> AggLabels
    {
        get { return myAggLabels; }
    }

    private ObservableCollection<ContactList> myContactLists;

    public IEnumerable<ContactList> ContactLists
    {
        get { return myContactLists; }
    }

    public MainWindow()
    {
        GetData();
        this.InitializeComponent();

        // Insert code required on object creation below this point.
    }

    public void GetData()
    {
        myAggLabels = new ObservableCollection<AggregatedLabel>();
        myContactLists = new ObservableCollection<ContactList>();

        DB2Connection conn = null;
        try
        {
            conn = new DB2Connection("XXXX;");
        }
        catch (Exception ex)
        {
            System.Windows.MessageBox.Show(ex.Message + " " + ex.InnerException);
        }

        //get all contactLists and their labels
        DB2Command command = new DB2Command("SQL SELECT statement");
        command.Connection = conn;

        conn.Open();

        //get all labels from database
        using (DB2DataReader dr = command.ExecuteReader())
        {
            while (dr.Read())
            {
                AggregatedLabel aggLabel = new AggregatedLabel();

                aggLabel.ID = Convert.ToInt32(dr["LABEL_ID"]);
                aggLabel.Name = dr["LABEL_NAME"].ToString();

                myAggLabels.Add(aggLabel);

            }
        }
        //Add unique contactLists to dictionary
        Dictionary<int, ContactList> myContactDictionary = new Dictionary<int, ContactList>();

        using (DB2DataReader dr = command.ExecuteReader())
        {
            while (dr.Read())
            {
               int id = Convert.ToInt32(dr["CONTACT_LIST_ID"]);

                if (!myContactDictionary.ContainsKey(id))
                {

                    ContactList contactList = new ContactList();

                    contactList.ContactListID = id;
                    contactList.ContactListName = dr["CONTACT_LIST_NAME"].ToString();
                    contactList.AggLabels = new ObservableCollection<AggregatedLabel>()
                {
                    new AggregatedLabel()
                    {
                        ID = Convert.ToInt32(dr["LABEL_ID"]),
                        Name = dr["LABEL_NAME"].ToString()
                    }

                };
                    myContactDictionary.Add(id, contactList);
                }
                else
                {
                    //populate existing contact lists with remaining labels
                    ContactList contactList = myContactDictionary[id];

                    contactList.AggLabels.Add
                    (
                        new AggregatedLabel() 
                        {
                            ID = Convert.ToInt32(dr["LABEL_ID"]),
                            Name = dr["LABEL_NAME"].ToString()
                        }
                    );
                }
            }
        }

        //add to observable collection      
        foreach (KeyValuePair<int, ContactList> contactKeyValue in myContactDictionary)
        {
            ContactList contactList = contactKeyValue.Value;

            myContactLists.Add(contactList);
        }

        conn.Close();        
    }
}

Answer 1

You should make a class for this, and just move all of your code into it.

Then create an instance of the class and set it as the DataContext for this Window.

If your interested in the mechanics, and the motivation (other than just pulling out of code behind), you can refer to my series on MVVM, or one of the many great MVVM introductions.

---

For example, your code above could be:

namespace Contact_Interests
{
    public partial class MainWindowViewModel // : INotifyPropertyChanged
    {
        private ObservableCollection<AggregatedLabel> myAggLabels;

        public ObservableCollection<AggregatedLabel> AggLabels
        {
            get { return myAggLabels; }
        }

        private ObservableCollection<ContactList> myContactLists;

        public IEnumerable<ContactList> ContactLists
        {
            get { return myContactLists; }
        }

        public MainWindowViewModel()
        {
            GetData();

            // Insert code required on object creation below this point.
        }

        public void GetData()
        {
            myAggLabels = new ObservableCollection<AggregatedLabel>();
            myContactLists = new ObservableCollection<ContactList>();

            DB2Connection conn = null;
            try
            {
                conn = new DB2Connection("XXXX;");
            }
            catch (Exception ex)
            {
                System.Windows.MessageBox.Show(ex.Message + " " + ex.InnerException);
            }

            //get all contactLists and their labels
            DB2Command command = new DB2Command("SQL SELECT statement");
            command.Connection = conn;

            conn.Open();

            //get all labels from database
            using (DB2DataReader dr = command.ExecuteReader())
            {
                while (dr.Read())
                {
                    AggregatedLabel aggLabel = new AggregatedLabel();

                    aggLabel.ID = Convert.ToInt32(dr["LABEL_ID"]);
                    aggLabel.Name = dr["LABEL_NAME"].ToString();

                    myAggLabels.Add(aggLabel);

                }
            }
            //Add unique contactLists to dictionary
            Dictionary<int, ContactList> myContactDictionary = new Dictionary<int, ContactList>();

            using (DB2DataReader dr = command.ExecuteReader())
            {
                while (dr.Read())
                {
                   int id = Convert.ToInt32(dr["CONTACT_LIST_ID"]);

                    if (!myContactDictionary.ContainsKey(id))
                    {

                        ContactList contactList = new ContactList();

                        contactList.ContactListID = id;
                        contactList.ContactListName = dr["CONTACT_LIST_NAME"].ToString();
                        contactList.AggLabels = new ObservableCollection<AggregatedLabel>()
                    {
                        new AggregatedLabel()
                        {
                            ID = Convert.ToInt32(dr["LABEL_ID"]),
                            Name = dr["LABEL_NAME"].ToString()
                        }

                    };
                        myContactDictionary.Add(id, contactList);
                    }
                    else
                    {
                        //populate existing contact lists with remaining labels
                        ContactList contactList = myContactDictionary[id];

                        contactList.AggLabels.Add
                        (
                            new AggregatedLabel() 
                            {
                                ID = Convert.ToInt32(dr["LABEL_ID"]),
                                Name = dr["LABEL_NAME"].ToString()
                            }
                        );
                    }
                }
            }

            //add to observable collection      
            foreach (KeyValuePair<int, ContactList> contactKeyValue in myContactDictionary)
            {
                ContactList contactList = contactKeyValue.Value;

                myContactLists.Add(contactList);
            }

            conn.Close();        
        }
    }
}

Then, your main window becomes:

namespace Contact_Interests
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
         public MainWindow()
         {
              InitializeComponent();
              this.DataContext = new MainWindowViewModel();
         }
     }
 }