Notify one object when changing the property of another object

Question

I have a parent object called a page that has a list of objects called Control:

public class Page { List<CustomControl> controls {get;set;} } 

The CustomControl class has the following settings:

 public class CustomControl { string Name {get;set;} string Value {get;set;} } 

Say, for example, that the page class has two CustomControl A and B. Is it possible to notify the user control B when the value of the Custom Control A property changes so that it can change some of its properties.

I was thinking of implementing the INotifyPropertyChanged event in the CustomControl class, as now I can notify the CustomControl instance when another instance of the same class has some property of its Modified.

Answer 1

 public class CustomControl : INotifyPropertyChanged { private string _name; public string Name { get { return _name; } set { if (_name == value) return; _name = value; PropertyChanged(this, new PropertyChangedEventArgs("Name")); } } private string _value; public string Value { get { return _value; } set { if (_value == value) return; _value = value; PropertyChanged(this, new PropertyChangedEventArgs("Value")); } } public event PropertyChangedEventHandler PropertyChanged = delegate { }; internal virtual void OnSiblingInPagePropertyChanged(object sender, PropertyChangedEventArgs args) { } } public class CustomControlObservableColletion : ObservableCollection<CustomControl> { // Required because, by default, it is not possible to find out which items // have been cleared when the CollectionChanged event is fired after a .Clear() call. protected override void ClearItems() { foreach (var item in Items.ToList()) Remove(item); } } public class Page { public IList<CustomControl> Controls { get; private set; } public Page() { var controls = new CustomControlObservableColletion(); controls.CollectionChanged += OnCollectionChanged; Controls = controls; } private void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e) { switch (e.Action) { case NotifyCollectionChangedAction.Add: RegisterControls(e.NewItems); break; case NotifyCollectionChangedAction.Replace: RegisterControls(e.NewItems); DeRegisterControls(e.OldItems); break; case NotifyCollectionChangedAction.Remove: DeRegisterControls(e.OldItems); break; } } private void RegisterControls(IList controls) { foreach (CustomControl control in controls) control.PropertyChanged += OnControlPropertyChanged; } private void DeRegisterControls(IList controls) { foreach (CustomControl control in controls) control.PropertyChanged -= OnControlPropertyChanged; } private void OnControlPropertyChanged(object sender, PropertyChangedEventArgs e) { foreach (var control in Controls.Where(c => c != sender)) control.OnSiblingInPagePropertyChanged(sender, e); } } 

Answer 2

 using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace PropertyNotificatioDemo { class Program { static void Main(string[] args) { PropertyNotification notification = new PropertyNotification(); //Create an object of PropertyNotification class. //Create EmployeeValueChange handler. PropertyNotification.EmployeeValueChange += new PropertyNotification.EmployeeNameHandler(PropertyNotification_EmployeeValueChange); //Display a message. Console.Write("Enter Value : "); //Read a value and initilize it in property. notification.EmployeeName = Console.ReadLine(); } //Handler for property notification is created. static void PropertyNotification_EmployeeValueChange(object sender, EventArgs e) { Console.WriteLine("Employee name is changed."+sender); } } public class PropertyNotification { //Create a private variable which store value. private static string _employeeName; //Create a delegate of named EmployeeNamed=Handler public delegate void EmployeeNameHandler(object sender, EventArgs e); //Create a event variable of EmployeeNameHandler public static event EmployeeNameHandler EmployeeValueChange; //Create a static method named OnEmployeeNameChanged public static void OnEmployeeNameChanged(EventArgs e) { if (EmployeeValueChange != null) EmployeeValueChange(_employeeName, e); } //Create a property EmployeeName public string EmployeeName { get { return _employeeName; } set { //Check if value of property is not same. if (_employeeName != value) { OnEmployeeNameChanged(new EventArgs()); _employeeName = value; } } } } }