鼠类：

public class Mouse
{
public string Name { get; set; }
public Mouse(Cat cat)
{
cat.Scream += new Cat.ScreamEventHandler(cat_Scream);
cat.Scream += this.RunAway;
}
public void RunAway(object sender， ScreamEventArgs e)
{
Cat c = (Cat)sender;
Console.WriteLine("{0} coming，she said:"{1}"，{2} running!(Running...)"， c.Name， e.Msg， this.Name);
}
void cat_Scream(object sender， ScreamEventArgs e)
{
Cat c = (Cat)sender;
Console.WriteLine("{0} coming，she said:"{1}"，{2} running!"， c.Name， e.Msg， this.Name);
}
}

　　这里的委托定义和.net Framework 类库定义方式相同，有助于了解系统提供的委托机制，所以还有一个猫叫事件的参数类：

public class ScreamEventArgs
{
public readonly string Msg;
public ScreamEventArgs(string msg)
{
this.Msg = msg;
}
}