将可观察集合绑定到XAML中的ListBox

Question

I've spent lots of hours with this problem.

I have a class with data:

public class User : INotifyPropertyChanged
{
    private int _key;
    private string _fullName;
    private string _nick;

    public int Key
    {
        get{return _key;}
        set { _key = value; NotifyPropertyChanged("Key"); }
    }
    public string Nick
    {
        get { return _nick; }
        set { _nick = value; NotifyPropertyChanged("Nick"); }
    }
    public string FullName
    {
        get { return _fullName; }
        set { _fullName = value; NotifyPropertyChanged("FullName"); }
    }


    public User()
    {
        Nick = "nickname";
        FullName = "fullname";
    }

    public User(String nick, String name, int key)
    {
        Nick = nick;
        FullName  = name;
    }


    //INotifyPropertyChanged implementation
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(String propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public override string ToString() 
    { 
        return string.Format("{0} {1}, {2}", Key, Nick, FullName); 
    }

}

Next I have a class with observablecollection of userClass class:

public class UserList : ObservableCollection<UserList>
{
    public UserList (){}

    ~UserList ()
    {
        //Serialize();
    }

    public void Serialize(ObservableCollection<UserList> usersColl) 
    {
        FileStream fs = new FileStream("DataFile.dat", FileMode.Create);
        BinaryFormatter formatter = new BinaryFormatter();
        try
        {
            formatter.Serialize(fs, usersColl);
        }
        catch (SerializationException e)
        {
            Console.WriteLine("Failed to serialize. Reason: " + e.Message);
            throw;
        }
        finally
        {
            fs.Close();
        }
    }

    public void Deserialize() 
    {
        FileStream fs = new FileStream("DataFile.dat", FileMode.Open);
        try 
        {
            BinaryFormatter formatter = new BinaryFormatter();
            //users = (Hashtable) formatter.Deserialize(fs);
            //usersColl = (ObservableCollection<userClass>)formatter.Deserialize(fs);
        }
        catch (SerializationException e) 
        {
            MessageBox.Show(" Error: " + e.Message);
            throw;
        }
        finally 
        {
            fs.Close();
        }
    }

}

In fact, after lots of testing an editing, big part of code doesn't work, like serialization. But it is not necessary for data binding and binding is what i am solving now.

So i have this collection and want to bind it to listBox. I tried several ways, but haven't got it to work.

The last one I tried gave me the write error:

The resource 'users' cannot be resolved.

<ListBox Grid.Column="0" Name="userViewLeft" ItemsSource="{Binding Source={StaticResource users} }" />

Answer 1

Some points to be noted

• Make Properties public and not private .
• Make Variables private .
• Follow Naming Conventions and don't append class behind the class.
• ItemsSource you supply should be as per scope of the data, In my example the userlist in class scope and I have provided the ItemSource on Window Loaded event.

Here is the an complete example code, In this I have nested the Grid Control inside ListBox because later on you can change the ListBox property for VirtualizingStackPanel. So that it would give huge performance gain when you have heavy updates on the list. Also you can use BindingList which is in my opinion better than ObservableCollection performance wise.

User class:

    public class User : INotifyPropertyChanged
    {
        private int _key;
        private string _fullName;
        private string _nick;

        public int Key
        {
            get { return _key; }
            set { _key = value; NotifyPropertyChanged("Key"); }
        }
        public string NickName
        {
            get { return _nick; }
            set { _nick = value; NotifyPropertyChanged("NickName"); }
        }
        public string Name
        {
            get { return _fullName; }
            set { _fullName = value; NotifyPropertyChanged("Name"); }
        }

        public User(String nick, String name, int key)
        {
            this.NickName = nick;
            this.Name = name;
            this.Key = key; 
        }

        public event PropertyChangedEventHandler PropertyChanged;
        private void NotifyPropertyChanged(String propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public override string ToString()
        {
            return string.Format("{0} {1}, {2}", Key, NickName, Name);
        }
    }

User List class:

    public class Users : ObservableCollection<User>
    {
        public Users()
        {
            Add(new User("Jamy", "James Smith", Count));
            Add(new User("Mairy", "Mary Hayes", Count));
            Add(new User("Dairy", "Dary Wills", Count));
        }
    }

XAML:

   <Grid>
        <Button Content="Start" Height="23" HorizontalAlignment="Left" Margin="416,12,0,0" x:Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" />
        <ListBox x:Name="UserList" HorizontalContentAlignment="Stretch" Margin="12,41,12,12">
            <ListBox.ItemTemplate>
                <DataTemplate>
                        <Grid Margin="10">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="20" />
                                <ColumnDefinition Width="150" />
                                <ColumnDefinition Width="*" />
                            </Grid.ColumnDefinitions>
                            <TextBlock Text="{Binding Key}" Margin="3" Grid.Column="0" />
                            <TextBlock Text="{Binding NickName}" Margin="3" Grid.Column="1" />
                            <TextBlock Text="{Binding Name}" Margin="3" Grid.Column="2" />
                        </Grid>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>

XAML Code behind:

public partial class MainWindow : Window
{
    public static Users userslist = new Users();
    DispatcherTimer timer = new DispatcherTimer();

    public MainWindow()
    {
        InitializeComponent();
        this.Loaded += new RoutedEventHandler(MainWindow_Loaded);
    }

    void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        timer.Interval = DateTime.Now.AddSeconds(10) - DateTime.Now;
        timer.Tick += new EventHandler(timer_Tick);
        UserList.ItemsSource = userslist;
    }

    void timer_Tick(object sender, EventArgs e)
    {
        userslist.Add(new User("Jamy - " + userslist.Count, "James Smith", userslist.Count));
        userslist.Add(new User("Mairy - " + userslist.Count, "Mary Hayes", userslist.Count));
        userslist.Add(new User("Dairy - " + userslist.Count, "Dary Wills", userslist.Count));
    }

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        if (button1.Content.ToString() == "Start")
        {
            button1.Content = "Stop";
            timer.Start();
        }
        else
        {
            button1.Content = "Start";
            timer.Stop();
        }
    }

}

Answer 2

You need to do 2 things:

Firstly, set the DataContext of whatever element ( Window / UserControl /whatever) contains your ListBox to an object that looks like:

public class ViewModel
{
    public ViewModel() { this.users = new userListClass(); }
    public userListClass users { get; private set; }
}

This is your view model, and it is what you want to bind to.

Secondly, change your binding to ItemsSource="{Binding Path=users}" . This translates into "set the value of my ItemsSource property to the value of the property users on this.DataContext . Because the DataContext is inherited from the parent, and you set this to the ViewModel class above, your ListBox will now display your user list.