c#开发学生成绩管理系统

    using System;
    using System.Collections.Generic;
    using System.Text;
    using System.IO;
    namespace programe_student
    {
        public struct student
        {
            public string student_id;
            public string student_name;
            public string student_course;
            public double student_score;
        };
        public class studentinformation
        {
            static FileStream F;
            StreamWriter W;
            StreamReader R;
            public void Add()
            {
                student S ;
                F = new FileStream("wang.txt", FileMode.Append, FileAccess.Write);
                W = new StreamWriter(F);
                Console.WriteLine("please Enter the information of the student.");
                Console.Write("student ID:");
                S.student_id = Console.ReadLine();
                W.Write("studentID:");
                W.Write(S.student_id);
                W.Write(",");
                Console.Write("student Name:");