How to update UI when ObservableCollection updated?

Question

I have simple app, where ObservableCollection is updating in code and when new item added the UI is updated too. To update UI i am using a Dispatcher which is passed as a property to ViewModel. My code is works, but i don't know right i am or not.

Here is the code:

MainWindow.xaml.cs

/// <summary>
/// Логика взаимодействия для MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    MainWindowViewModel model = new MainWindowViewModel();

    public MainWindow()
    {
        InitializeComponent();
        this.DataContext = model;
        this.model.dispatcher = this.Dispatcher;    
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        string url = urlToCheck.Text;

        Task task = new Task(() =>
        {
            model.GetUrls(url);
        });

        task.ContinueWith((previousTask) =>
        {
            label.Content = "Все ссылки собраны.";
        },
        TaskScheduler.FromCurrentSynchronizationContext());

        label.Content = "Идёт сбор ссылок...";
        task.Start();
    }
}

MainWindowViewModel.cs

 class MainWindowViewModel
{
    public ObservableCollection<Url> Urls { get; set; }
    public bool NeedToGetResponseForChildUrls { get; set; }
    public bool NeedToDeletePreviousResults { get; set; }
    public Dispatcher dispatcher;

    some code.....................


        **and something like this i am updating ObservableCollection:**

        if (NeedToDeletePreviousResults)
            {
                dispatcher.Invoke(() =>
                {
                    Urls.Clear();
                });

            }

Url.cs

    using System.Collections.ObjectModel;
using System.ComponentModel;

namespace CheckUrl
{
    public class Url : INotifyPropertyChanged
    {
        private string _absoluteUrl;
        public string AbsoluteUrl
        {
            get { return _absoluteUrl; }
            set
            {
                if (_absoluteUrl != value)
                {
                    _absoluteUrl = value;
                    OnPropertyChanged("AbsoluteUrl");
                }
            }
        }

        private int _responseStatusCode;
        public int ResponseStatusCode
        {
            get { return _responseStatusCode; }
            set
            {
                if (_responseStatusCode != value)
                {
                    _responseStatusCode = value;
                    OnPropertyChanged("ResponseStatusCode");
                }
            }
        }

        private string _responseStatusDescription;
        public string ResponseStatusDescription
        {
            get { return _responseStatusDescription; }
            set
            {
                if (_responseStatusDescription != value)
                {
                    _responseStatusDescription = value;
                    OnPropertyChanged("ResponseStatusDescription");
                }
            }
        }

        public enum Status { Working, Broken };

        private Status _urlStatus;
        public Status UrlStatus
        {
            get { return _urlStatus; }
            set
            {
                if (_urlStatus != value)
                {
                    _urlStatus = value;
                    OnPropertyChanged("UrlStatus");
                }
            }
        }

        private string _color;
        public string Color
        {
            get { return _color; }
            set
            {
                if (_color != value)
                {
                    _color = value;
                    OnPropertyChanged("Color");
                }
            }
        }

        private ObservableCollection<ChildUrl> _childUrlsValue = new ObservableCollection<ChildUrl>();
        public ObservableCollection<ChildUrl> ChildUrls
        {
            get
            {
                return _childUrlsValue;
            }
            set
            {
                _childUrlsValue = value;
            }
        }

        /// <summary>
        /// Конструктор класса Url.
        /// </summary>
        public Url(string absoluteUrl, int responseStatusCode, string responseStatusDescription, Status urlStatus, string color)
        {
            this.AbsoluteUrl = absoluteUrl;
            this.ResponseStatusCode = responseStatusCode;
            this.ResponseStatusDescription = responseStatusDescription;
            this.UrlStatus = urlStatus;
            this.Color = color;
        }

        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            { 
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}

Answer 1

ObservableCollection can update your UI automaticaly by using binding. Use a list of ObservableCollection and add / remove items from is. Make the ObservableCollection as a public property.In the MainWindow constructor write:

This.DataContext=This;

Use binding to your listBox / any other control you need to show the items on. ObservableCollection allready implement IINotifyPropertyChanged in it. Once you change the items in your ObservableCollection your UI will change as well.