.NET 4.0 New Feature - IObservablelt;Tgt; amp; IObserverlt;Tgt;

    public Unsubscriber(List<IObserver<T>> observers, IObserver<T> observer)
    {
        this.m_Observers = observers;
        this.m_Observer = observer;
    }

    public void Dispose()
    {
        if (m_Observer != null && m_Observers.Contains(m_Observer))
        {
            m_Observers.Remove(m_Observer);
        }
    }
}</pre>

public class Observable<T> : IObservable<T> { #region Class private class Unsubscriber : IDisposable { private List<IObserver<T>> m_Observers { get; set; } private IObserver<T> m_Observer { get; set; }

    public Unsubscriber(List<IObserver<T>> observers, IObserver<T> observer)
    {
        this.m_Observers = observers;
        this.m_Observer = observer;
    }

    public void Dispose()
    {
        if (m_Observer != null && m_Observers.Contains(m_Observer))
        {
            m_Observers.Remove(m_Observer);
        }
    }
}
#endregion

#region Enum
enum NotifyType
{
    Next,
    Completed,
    Error
}
#endregion

#region Var
private List<IObserver<T>> _observers;
#endregion

#region Protected Property
protected List<IObserver<T>> m_Observers
{
    get
    {
        if (_observers == null)
            _observers = new List<IObserver<T>>();
        return _observers;
    }
}
#endregion

#region Private Method
private void NotifyError(Exception error)
{
    foreach (IObserver<T> observer in m_Observers)
    {
        observer.OnError(error);
    }
}
#endregion


#region Protected Method
protected void NotifyNext(T obj)
{
    try
    {
        foreach (IObserver<T> observer in m_Observers)
        {
            observer.OnNext(obj);
        }
    }
    catch (Exception e)
    {
        NotifyError(e);
    }
}

protected void NotifyCompleted()
{
    try
    {
        foreach (IObserver<T> observer in m_Observers)
        {
            observer.OnCompleted();
        }
    }
    catch (Exception e)
    {
        NotifyError(e);
    }
}
#endregion


#region Public Method
public IDisposable Subscribe(IObserver<T> observer)
{
    if (!m_Observers.Contains(observer))
    {
        m_Observers.Add(observer);
    }
    return new Unsubscriber(m_Observers, observer);
}
#endregion

}

namespace ConsoleApplication5 { class Program { static void Main(string[] args) { BlogViwer guest = new BlogViwer(); Blog levelUp = new Blog(“Level Up”, “Larry Nung”); levelUp.Subscribe(guest); levelUp.AddArticle(".NET 4.0 New Feature - Environment.Is64BitProcess & Environment.Is64BitOperatingSystem", “…”); levelUp.AddArticle(“LINQ to CSV library”, “…”); levelUp.AddArticle("[C#][VB.NET]最大公因數 & 最小公倍數", “…”); } }

class Blog : Observable<string>
{
    List<string> _articles;
    private List<string> Articles
    {
        get
        {
            if (_articles == null)
                _articles = new List<string>();
            return _articles;
        }
    }

    public String Name { get; set; }
    public String Owner { get; set; }

    public Blog(String name, string owner)
    {
        this.Name = name;
        this.Owner = owner;
    }

    public void AddArticle(string title, string content)
    {
        string article = title + Environment.NewLine + content;
        Articles.Add(article);
        NotifyNext(article);
    }
}

class BlogViwer : IObserver<string>
{
    public void OnCompleted()
    {
        Console.WriteLine("Completed...");
    }

    public void OnError(Exception error)
    {
        Console.WriteLine("Error...");
    }

    public void OnNext(string value)
    {
        Console.WriteLine(value);
        Console.WriteLine(new string('"', 50));
    }
}

}

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