static void Main(string[] args)
        {
            SayHello("侯志强", 80);
            SayHello("侯志强");

            Console.ReadKey();
        }

        C#4.0实现参数的默认值
        static void SayHello(string strName,int nAge=20)
        {
            Console.WriteLine("我的名字是{0}，今年{1}岁", strName, nAge);
        }

        //C#4.0以前实现参数默认值
        static void SayHello(string strName1, int nAge)
        {
            Console.WriteLine("我的名字是{0}，今年{1}岁", strName1, nAge);
        }

        static void SayHello(string strName1)
        {
            SayHello(strName1, 20);
        }