OptionParameter

using System;

namespace OptionalParameter
{
    class Program
    {
        static void Main(string[] args)
        {
            DisplayGreeting(firstName: "Wu", lastName: "Hui");
        }

        static void DisplayGreeting(string firstName, string lastName,string middleName = "Guang")
        {
            Console.WriteLine("You input the Full name is :{0},{1},{2}", firstName, middleName, lastName);
        }
    }
}

运行结果：

You input the Full name is :Wu,Guang,Hui
请按任意键继续. . .

如果在调用DisplayGreeting方法的时候，没有为可选参数赋值，那么运行结果显示默认参数赋值，如上图所示；如果为可选参数赋了值，则会覆盖默认参数赋值，显示最新的结果。如下图所示：

using System;

namespace OptionalParameter
{
    class Program
    {
        static void Main(string[] args)
        {
            DisplayGreeting(firstName: "Wu", middleName:"Zhi",lastName: "Hui");
        }

        static void DisplayGreeting(string firstName, string lastName,string middleName = "Guang")
        {
            Console.WriteLine("You input the Full name is :{0},{1},{2}", firstName, middleName, lastName);
        }
    }
}

运行结果如下：

You input the Full name is :Wu,Zhi,Hui
请按任意键继续. . .