C# 事件 EventHanlder

using System;
 
public class CharEventArgs : EventArgs
{
    public char CurrChar;
    public CharEventArgs(char CurrChar)
    {
        this.CurrChar = CurrChar;
    }
}
 
class CharChecker
{
    public event EventHandler<CharEventArgs> CharTest;
    public CharEventArgs myeven;
    char curr_char;
    public char Curr_Char
    {
        get { return curr_char; }
        set 
        {
            if (CharTest != null)
            {
                myeven = new CharEventArgs(value);
                curr_char = value;
                CharTest(this, myeven);
            }
        }
    }
}
 
class AppEvent
{
    static void Main()
    {
        CharChecker chartester = new CharChecker();
        chartester.CharTest += new EventHandler<CharEventArgs>(Charge_X);
        chartester.Curr_Char = 'a';
        Console.WriteLine("event handler result: {0}", chartester.myeven.CurrChar);
        chartester.Curr_Char = 'x';
        Console.WriteLine("event handler result: {0}", chartester.myeven.CurrChar);
        Console.WriteLine();
    }
 
    static void Charge_X(object sender,CharEventArgs e)
    {
        CharChecker cc = (CharChecker)sender;
        if (e.CurrChar == 'x')
        {
            Console.Write("trigger char is x,");
            e.CurrChar = '?';
        }
        else
        {
            Console.Write("trigger char is not x,");
        }
    }
}