有没有哪位大哥能帮我把这个程序完善了（C#学生成绩管理系统）

[Just小布]

using System;
using System.IO;
public class StudentInfo
{
private int id;
private string name;
private float english;
private float math;
public int ID
{
get
{
return this.id;
}
set
{
this.id = value;
}
}

public string Name
{
get
{
return this.name;
}
set
{
this.name = value;
}
}



public float English
{
get
{
return this.english;
}
set
{
this.english = value;
}
}
public float Math
{
get
{
return this.math;
}
set
{
this.math = value;
}
}
public float PJ()
{

return (english + math)/2;
}
}


public class StudentDAL // 学生数据管理类
{
const int MAX = 30;

int count = 0;

StudentInfo[] students = new StudentInfo[MAX];


public StudentInfo[] Students
{
get
{
return students;
}
}


public int Count
{
get
{
return this.count;
}
}


public bool Insert(StudentInfo stu)// 添加一个学生
{
if (Count < MAX)
{
students[this.count] = stu;//插入学生信息
this.count++;
return true;
}
return false;
}



public StudentInfo[] FindID(int id) //通过学号找
{
StudentInfo[] stu = new StudentInfo[MAX];
int count = 0;
for (int i = 0; i < Count; i++)
{
if (students[i].ID == id)
{
stu[count] = students[i];
count++;

}

}
if (count > 0) //找到了
{
StudentInfo[] temp = new StudentInfo[count];
for (int i = 0; i < count; i++)
{
temp[i] = stu[i];
}
return temp;
}

return null;
}

public StudentInfo[] FindByName(string name) //通过姓名找
{
StudentInfo[] stu = new StudentInfo[MAX];
int count = 0;
for (int i = 0; i < Count; i++)
{
if (students[i].Name == name)
{
stu[count] = students[i];
count++;
}
}
if (count > 0)
{
StudentInfo[] temp = new StudentInfo[count]; //有几个相同就把几个加入数组
for (int i = 0; i < count; i++)
{
temp[i] = stu[i];
}
return temp;
}
return null;
}

public class StudentBLL //操作
{
StudentDAL stuDAL = new StudentDAL();

public bool Insert(StudentInfo stu)
{
while (this.FindID(stu.ID) != null)
{
Console.Write("对不起，该学号已存在，请输入一个新的学号：");
stu.ID = int.Parse (Console .ReadLine ());
}
return stuDAL.Insert(stu);
}


public StudentInfo[] FindID(int id)
{
return stuDAL.FindID(id);
}


public StudentInfo[] FindByName(string name)
{
return stuDAL.FindByName(name);
}

public void PrintHead()
{
Console.WriteLine("学号\t姓名\t英语成绩\t数学成绩\t平均成绩");
}

public void Print(StudentInfo stu)
{
Console.WriteLine("{0}\t{1}\t{2}\t\t{3}\t\t{4}", stu.ID, stu.Name, stu.English, stu.Math, stu.PJ());
}


public void Print(StudentInfo[] stus)
{
foreach (StudentInfo stu in stus)
{
this.Print(stu);
}
}


public void Print()
{
if (stuDAL.Count > 0)
{
this.PrintHead();
for (int i = 0; i < stuDAL.Count; i++)
{
this.Print(stuDAL.Students[i]);
}
Console.WriteLine("当前共有{0}名学生。", stuDAL.Count);
}
else
{
Console.WriteLine("对不起，当前还没有学生信息。。。");
}
}

public StudentInfo GenStudentInfo(bool needID)
{
StudentInfo info = new StudentInfo();
if (needID)
{
Console.Write("请输入学生的学号：");
info.ID = int.Parse(Console.ReadLine());
}
Console.Write("请输入学生的姓名：");
info.Name = Console.ReadLine();
Console.Write("请输入学生的英语成绩：");
info.English = float.Parse(Console.ReadLine());
Console.Write("请输入学生的数学成绩");
info.Math = float.Parse(Console.ReadLine());
return info;
}
public StudentInfo GenStudentInfo()
{
return this.GenStudentInfo(true);
}

}

class Program
{
static void Main(string[] args)
{
StudentBLL stuBLL = new StudentBLL();

StudentInfo[] infos;
Console.WriteLine("-------------------学生成绩管理系统-------------------");
while (true)
{
Console.WriteLine("请按键选择您要进行的操作：");
Console.WriteLine("1.添加一个学生 2.查看所有学生信息");
Console.WriteLine("3.通过姓名查找学生 4.通过学号查找学生");
Console.WriteLine("5.英语平均分 6.数学平均分");
Console.WriteLine("7.英语最高分 8.数学最高分");
Console.WriteLine("q.退出程序");
switch (Console.ReadLine())
{
case "1":
if (stuBLL.Insert(stuBLL.GenStudentInfo()))
{
Console.WriteLine("添加成功。");
}
else
{
Console.WriteLine("添加失败，学生信息表已满。");
}
break;
case "2":
stuBLL.Print();
break;
case "3":
Console.Write("请输入要查找的学生的姓名：");
infos = stuBLL.FindByName(Console.ReadLine());
if (infos == null)
{
Console.WriteLine("对不起，您查找的学生不存在。");
}
else
{
stuBLL.PrintHead();
stuBLL.Print(infos);
}
break;

case "4":
Console.Write("请输入要查找的学生的学号：");
infos = stuBLL.FindID(int.Parse(Console.ReadLine()));
if (infos == null)
{
Console.WriteLine("对不起，您查找的学生不存在。");
}
else
{
stuBLL.PrintHead();
stuBLL.Print(infos);
}
break;
case "5":
{ }
break;
case "6":
{ }
break;
case "7":
{ }
break;
case "8":
{ }
break;

case "q":
return;
default:
Console.WriteLine("输入有误，请重新输入。");
break;
}
Console.WriteLine("按任意键继续(q键退出)...");
Console.ReadKey();
}
}
}
}

[TNight]

using System;
using System.IO;
  public class StudentInfo
  {
  private int id;
  private string name;
  private float english;
  private float math;
  public int ID
  {
  get
  {
  return this.id;
  }
  set
  {
  this.id = value;
  }
  }

  public string Name
  {
  get
  {
  return this.name;
  }
  set
  {
  this.name = value;
  }
  }



  public float English
  {
  get
  {
  return this.english;
  }
  set
  {
  this.english = value;
  }
  }
  public float Math
  {
  get
  {
  return this.math;
  }
  set
  {
  this.math = value;
  }
  }
  public float PJ()
  {

  return (english + math)/2;
  }
  }

    
  public class StudentDAL // 学生数据管理类
  {
  const int MAX = 30;

  int count = 0;

  StudentInfo[] students = new StudentInfo[MAX];


  public StudentInfo[] Students
  {
  get
  {
  return students;
  }
  }


  public int Count
  {
  get
  {
  return this.count;
  }
  }


  public bool Insert(StudentInfo stu)// 添加一个学生
  {
  if (Count < MAX)   
  {
  students[this.count] = stu;//插入学生信息
  this.count++;
  return true;
  }
  return false;
  }



  public StudentInfo[] FindID(int id) //通过学号找
  {
  StudentInfo[] stu = new StudentInfo[MAX];
  int count = 0;
  for (int i = 0; i < Count; i++)
  {
  if (students[i].ID == id)
  {
  stu[count] = students[i];
  count++;
    
  }

  }  
  if (count > 0) //找到了
  {
  StudentInfo[] temp = new StudentInfo[count];   
  for (int i = 0; i < count; i++)
  {
  temp[i] = stu[i];
  }
  return temp;
  }

  return null;
  }

  public StudentInfo[] FindByName(string name) //通过姓名找
  {
  StudentInfo[] stu = new StudentInfo[MAX];
  int count = 0;
  for (int i = 0; i < Count; i++)
  {
  if (students[i].Name == name)
  {
  stu[count] = students[i];
  count++;
  }
  }
  if (count > 0)
  {
  StudentInfo[] temp = new StudentInfo[count]; //有几个相同就把几个加入数组
  for (int i = 0; i < count; i++)
  {
  temp[i] = stu[i];
  }
  return temp;
  }
  return null;
  }

  public class StudentBLL //操作
  {
  StudentDAL stuDAL = new StudentDAL();

  public bool Insert(StudentInfo stu)
  {
  while (this.FindID(stu.ID) != null)
  {
  Console.Write("对不起，该学号已存在，请输入一个新的学号：");
  stu.ID = int.Parse (Console .ReadLine ());
  }
  return stuDAL.Insert(stu);
  }


  public StudentInfo[] FindID(int id)
  {
  return stuDAL.FindID(id);
  }


  public StudentInfo[] FindByName(string name)
  {
  return stuDAL.FindByName(name);
  }

  public void PrintHead()
  {
  Console.WriteLine("学号\t姓名\t英语成绩\t数学成绩\t平均成绩");
  }

  public void Print(StudentInfo stu)
  {
  Console.WriteLine("{0}\t{1}\t{2}\t\t{3}\t\t{4}", stu.ID, stu.Name, stu.English, stu.Math, stu.PJ());
  }


  public void Print(StudentInfo[] stus)
  {
  foreach (StudentInfo stu in stus)
  {
  this.Print(stu);
  }
  }


  public void Print()
  {
  if (stuDAL.Count > 0)
  {
  this.PrintHead();
  for (int i = 0; i < stuDAL.Count; i++)
  {
  this.Print(stuDAL.Students[i]);
  }
  Console.WriteLine("当前共有{0}名学生。", stuDAL.Count);
  }
  else
  {
  Console.WriteLine("对不起，当前还没有学生信息。。。");
  }
  }

  public StudentInfo GenStudentInfo(bool needID)
  {
  StudentInfo info = new StudentInfo();
  if (needID)
  {
  Console.Write("请输入学生的学号：");
  info.ID = int.Parse(Console.ReadLine());
  }
  Console.Write("请输入学生的姓名：");
  info.Name = Console.ReadLine();
  Console.Write("请输入学生的英语成绩：");
  info.English = float.Parse(Console.ReadLine());
  Console.Write("请输入学生的数学成绩");
  info.Math = float.Parse(Console.ReadLine());
  return info;
  }
  public StudentInfo GenStudentInfo()
  {
  return this.GenStudentInfo(true);
  }

  }

  class Program
  {
  static void Main(string[] args)
  {
  StudentBLL stuBLL = new StudentBLL();
    
  StudentInfo[] infos;
  Console.WriteLine("-------------------学生成绩管理系统-------------------");
  while (true)
  {
  Console.WriteLine("请按键选择您要进行的操作：");
  Console.WriteLine("1.添加一个学生 2.查看所有学生信息");
  Console.WriteLine("3.通过姓名查找学生 4.通过学号查找学生");
  Console.WriteLine("5.英语平均分 6.数学平均分");
  Console.WriteLine("7.英语最高分 8.数学最高分");
  Console.WriteLine("q.退出程序");
  switch (Console.ReadLine())
  {
  case "1":
  if (stuBLL.Insert(stuBLL.GenStudentInfo()))
  {
  Console.WriteLine("添加成功。");
  }
  else
  {
  Console.WriteLine("添加失败，学生信息表已满。");
  }
  break;
  case "2":
  stuBLL.Print();
  break;
  case "3":
  Console.Write("请输入要查找的学生的姓名：");
  infos = stuBLL.FindByName(Console.ReadLine());
  if (infos == null)
  {
  Console.WriteLine("对不起，您查找的学生不存在。");
  }
  else
  {
  stuBLL.PrintHead();
  stuBLL.Print(infos);
  }
  break;
    
  case "4":
  Console.Write("请输入要查找的学生的学号：");
  infos = stuBLL.FindID(int.Parse(Console.ReadLine()));
  if (infos == null)
  {
  Console.WriteLine("对不起，您查找的学生不存在。");
  }
  else
  {
  stuBLL.PrintHead();
  stuBLL.Print(infos);
  }
  break;
  case "5":
  { }
  break;
  case "6":
  { }
  break;
  case "7":
  { }
  break;
  case "8":
  { }
  break;
    
  case "q":
  return;
  default:
  Console.WriteLine("输入有误，请重新输入。");
  break;
  }
  Console.WriteLine("按任意键继续(q键退出)...");
  Console.ReadKey();
  }
  }
  }
  }

要下班了，先看下