C # 4 observer implementation

Question

I want the button when it clicks a new line to be displayed in text boxes

what am I doing wrong

can somone tell me why this code is not working? ...

namespace WindowsFormsApplication1 { public partial class Form1 : Form { public event Startdelegate StartEvent; myButton button; newTb[] tb; public Form1() { InitializeComponent(); button = new myButton(); button.Parent = this; button.Location = new Point(120, 0); button.Text = "click on me!!!"; tb = new newTb[8]; for (int i = 0; i <= 80; i += 15) { tb[i / 15] = new newTb(); tb[i / 15].Parent = this; tb[i / 15].Location = new Point(i + i, i + i); // button.Subscribe(tb[i / 15]); } button.Click += new EventHandler(button_Click); } private void button_Click(object sender, EventArgs e) { button.s = "this is clicking"; //button.Notify(); } } public class myButton : Button, IObservable<newTb> { public string s; private List<IObserver<newTb>> observers; public myButton() { observers = new List<IObserver<newTb>>(); } public IDisposable Subscribe(IObserver<newTb> observer) { if (!observers.Contains(observer)) { observers.Add(observer); } return new Unsubscriber(observers, observer); } protected void Notify(newTb tb) { foreach (IObserver<newTb> observer in observers) { observer.OnNext(tb); } } #region Unsubscriber private class Unsubscriber : IDisposable { private List<IObserver<newTb>> observers; private IObserver<newTb> observer; public Unsubscriber(List<IObserver<newTb>> observers, IObserver<newTb> observer) { this.observers = observers; this.observer = observer; } public void Dispose() { if (observer != null && observers.Contains(observer)) { observers.Remove(observer); } } } #endregion class newTb : TextBox, IObserver<string> { string s; public void OnCompleted() { } public void OnError(Exception error) { } public void OnNext(string value) { this.Text = value; } } } } 

Answer 1

According to http://msdn.microsoft.com/en-us/library/dd783449.aspx

The IObserver and IObservable interfaces provide a generic push-based notification mechanism, also known as an observer design pattern. The IObservable interface represents a class that sends notifications (provider); The IObserver interface represents the class that receives them (observer).

T represents a class that provides notification information.

In your case, the information you pass is a message (string). In your example, you passed control newTB

With the following announcement

  public class ObservableButton : Button, IObservable<string> {} public class ObserverTextBox : TextBox, IObserver<string> {} 

Every thing gets into place.

The Notify of classObservableButton method can be written this way.

  public void Notify(string text) { foreach (IObserver<string> observer in _Observers) { observer.OnNext(text); } } 

Here is the full source code

 using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace ObservableDemo { public class ObservableButton : Button, IObservable<string> { private List<IObserver<string>> _Observers; public ObservableButton() { _Observers = new List<IObserver<string>>(); } IDisposable IObservable<string>.Subscribe(IObserver<string> observer) { if (!_Observers.Contains(observer)) { _Observers.Add(observer); } return new Unsubscriber(_Observers, observer); } public void Notify(string text) { foreach (IObserver<string> observer in _Observers) { observer.OnNext(text); } } private class Unsubscriber : IDisposable { private List<IObserver<string>> observers; private IObserver<string> observer; public Unsubscriber(List<IObserver<string>> observers, IObserver<string> observer) { this.observers = observers; this.observer = observer; } public void Dispose() { if (observer != null && observers.Contains(observer)) { observers.Remove(observer); } } } } } using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace ObservableDemo { public class ObserverTextBox : TextBox, IObserver<string> { private IDisposable unsubscriber; void IObserver<string>.OnCompleted() { } void IObserver<string>.OnError(Exception error) { } void IObserver<string>.OnNext(string value) { this.Text = value; this.Refresh(); } public virtual void Subscribe(IObservable<string> provider) { if (provider != null) unsubscriber = provider.Subscribe(this); } public virtual void Unsubscribe() { unsubscriber.Dispose(); } } } using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace ObservableDemo { public partial class Form1 : Form { ObservableButton button; public Form1() { InitializeComponent(); button = new ObservableButton(); button.Parent = this; button.Location = new Point(120, 0); button.Text = "click on me!!!"; button.Click += new EventHandler(button_Click); for (int i = 0; i < 8; i++) { ObserverTextBox tb = new ObserverTextBox(); tb.Parent = this; tb.Location = new Point(0 , 30+(i*30)); tb.Width = 300; tb.Subscribe(button); } } private void button_Click(object sender, EventArgs e) { button.Notify(String.Format("{0} this is the message", DateTime.Now)); } void Form1_Load(object sender, System.EventArgs e) { } } } 

Answer 2

I believe this may be your problem:

 class newTb : TextBox, IObserver<string> 

Because what you wanted to observe based on this sample:

 observers = new List<IObserver<newTb>>(); 

actually an IObserver <newTb>, which is different from an IObserver <string>. Your newTb class does not implement the first interface, it only implements the latter. Not sure why this compiles (if so).