private static void Main(string[] args)
{
Employee test = new Employee();
test.EmpInfo();
Console.WriteLine("------------------------");
DervEmployee objDervEmployee = new DervEmployee();
objDervEmployee.EmpInfo();
Console.WriteLine("------------------------");
//注意：objDervEmployee派生类的实例是赋给Employee类的objEmployee的引用，
// 所以objEmployee引用调用EmpInfo()方法时 还是调用DervEmployee类的方法
Employee objEmployee = objDervEmployee;
objEmployee.EmpInfo();
Console.ReadLine();
}
