创建控制台应用程序，在点击项目右键添加-新建项-类命名为: Program类，详细代码如下：

using System;

namespace Text_09_23Convert
{
    class Program
    {
        class Student
        {
            public string stuNo = "3119070130";
            public string Name;
            public string Sex;
      
            public double Math;
            public double Chi;
            public double Enl;
            public double tal()
            {
                double tal;
                //return Math+Chi+Enl;
                tal = Math + Chi + Enl;
                return tal;
            }
            public double avg()
            {
                double avg;
                avg = (Math + Chi + Enl) / 3;
                return avg;
            }
            public void input()
            {
                Console.WriteLine("请输入学号：");
                stuNo = Console.ReadLine();
                Console.WriteLine("请输入姓名");
                Name = Console.ReadLine();
                Console.WriteLine("请输入数学成绩：");
                Math = double.Parse(Console.ReadLine());
                Console.WriteLine("请输入英语成绩：");
                Enl = double.Parse(Console.ReadLine());
                Console.WriteLine("请输入语文成绩：");
                Chi = double.Parse(Console.ReadLine());
            }
        }
        static void Main(string[] args)
        {
            Student stu = new Student();
            stu.input();
            Console.WriteLine("{0}的总成绩为：{1},平均成绩为：{2}", stu.Name, stu.tal(), stu.avg());
            Console.ReadKey();
        }
    }
}

结果：