[.Net Concept]理解事件的宣告方式與用法

#region Event
event NameChangingEventHandler NameChanging;
event NameChangedEventHandler NameChanged;
#endregion</pre>

#region Event event EventHandler<FriendEventArgs> FriendAdded; #endregion

#region Protected Method protected void OnFriendAdded(FriendEventArgs e) { if (FriendAdded == null) return; FriendAdded(this, e); } #endregion

#region Public Method public void AddFriend(Person friend) { Friends.Add(friend); OnFriendAdded(new FriendEventArgs(friend.Name)); } #endregion

…

class FriendEventArgs : EventArgs { #region Var private String _name; #endregion

#region Property
public String Name
{
    get
    {
        if (_name == null)
            return String.Empty;
        return _name;
    }
    private set
    {
        _name = value;
    }
}
#endregion

#region Constructor
public FriendEventArgs(string name)
{
    this.Name = name;
}
#endregion

}

#region Protected Method
protected void OnNameChanging(EventArgs e)
{
    if (NameChanging == null)
        return;
    NameChanging(this, e);
}

protected void OnNameChanged(EventArgs e)
{
    if (NameChanged == null)
        return;
    NameChanged(this, e);
}
#endregion</pre>

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