程式碼如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var student1 = new studentName("hha", "wang");
            var student2 = new studentName { firstname = "hha", lastname = "wang" };
            var student3 = new studentName { ID = 20 };
            Console.WriteLine(student1.ToString());
            Console.WriteLine(student2.ToString());
            Console.WriteLine(student3.ToString());
            Console.ReadLine();
        }
    }
    public class studentName
    {
        public string firstname { get; set; }
        public string lastname{get; set;}
        
        public int ID {get;set;}

        public studentName()
        { }
        public studentName(string first,string last)
        {
            firstname = first;
            lastname = last;
        }
        public override string ToString()
        {
            return firstname + " " + ID;
        }
    }
}

 

執行效果如下：