将员工数据列表转换为单例类应用程序

Question

我在C#中制作了一个列表员工数据应用程序，其中包含AddEmployee，DeleteEmployee，SearchEmployee等功能。我想制作相同的程序，但使用单例设计模式。我知道 Singleton 的结构，但我搞砸了制作列表，然后将实际员工添加到列表中。

这是我程序的一部分：

class Student : IComparable<Student>
{
    //public int id;
    public string name;
    public decimal salary;
    public string position;
    public int intern;
    public Student(string name, string position, int intern, decimal salary)
    {
        this.name = name;
        this.position = position;
        this.intern = intern;
        this.salary = salary;
    }
public string Name { get; set; }
public decimal Salary { get; set; }
public string Position { get; set; }
public int Intern { get; set; }
    public void CalculateSalary()
    {
        salary = 1000 * intern;
    }
    public override string ToString()
    {
        return "Name: " + name + "t Position: " + position + "t Intern: " + intern + "t Salary: " + salary;
    }
    /// <summary>
    /// Gets student information from the user and adds a new student to the list
    /// </summary>
    /// <param name="existingStudents">The list of students to add to</param>
    private static void AddStudent(List<Student> existingStudents)
    {
        string ans = "";
        do{
            // Initialize the list if it's null
            if (existingStudents == null) existingStudents = new List<Student>();
            int tempInt;
            // Get student information from the user
            Console.WriteLine("Enter new student information");
            Console.Write(" 2. Enter student Name: ");
            var name = Console.ReadLine();
            Console.Write(" 3. Enter student Job Title: ");
            var jobTitle = Console.ReadLine();
            do
            {
                Console.Write(" 4. Enter student years of service: ");
            } while (!int.TryParse(Console.ReadLine(), out tempInt));
            var yrsOfService = tempInt;
            var salar = tempInt;
            // Add the new student to the list
            existingStudents.Add(new Student(name, jobTitle, yrsOfService, salar));
            foreach (Student stud in existingStudents)
            {
                stud.CalculateSalary();
                Console.WriteLine(stud.ToString());
            }
            Console.WriteLine("Do you want to add another Student? y/n");
            ans = Console.ReadLine();
        } 
        while (ans != "n");
    }

在主程序中，我有一个列表并调用 addStudent 函数：

             List<Student> st = new List<Student>();
        int answer = 1;
        do
        {
            Console.WriteLine("============================");
            Console.WriteLine("2. Read From File");
            Console.WriteLine("3. Add Student...");
            answer = Convert.ToInt32(Console.ReadLine());
            switch (answer)
            {
                case 2:
                    JustReadFromFile(st, filePath);
                    break;
                case 3:
                    AddStudent(st);
                    break;
                case 4:
                    Console.WriteLine("Exit Menu...");
                    break;
            }
        } while (answer != 4);

列表 st = 新列表((;

我知道我必须创建一个私有静态实例。

   private static Student st;

另外，应该有一个私人的学生构造函数，而不是我的上面。

   private Student() { }    

这就是创造我的新学生的方法。我也认为我需要类似的方法来创建我的列表，但我不确定。

   public static Student getInstance()
{
    if (st == null)
        st = new Student();
    return st;
}

你能给出一些方向和建议吗？谢谢

Answer 1

Student类：

public class Student
{
    public string Name { get; set; }
    public decimal Salary { get; set; }
    public string Position { get; set; }
    public int Intern { get; set; }
}

StudentData单例(您也可以将List<Student设为私有，并在 Singleton 类本身中创建方法来与列表交互并向其获取/添加数据，但为了示例的简单性，我将其公开(：

public class StudentData
{
    private static readonly StudentData _studentData = new StudentData();
    public List<Student> Students { get; set; }
    private StudentData()
    {
        Students = new List<Student>();
    }
    public static StudentData GetInstance()
    {
        return _studentData;
    }
}

用法如下：

        var studentData = StudentData.GetInstance();
        //Get all students in the singleton
        var students = studentData.Students;
        //Add new student
        studentData.Students.Add(new Student());
        studentData.Students.Add(new Student
        {
            Intern = 1,
            Name = "SomeName"
        });

希望这会让你走向正确的方向。

Answer 2

public class Student
{
    private static Student instance = null;
    private static readonly object locker = new object();
    public static Student Instance
    {
        get
        {
            lock (locker)
            {
                if (instance == null)
                {
                    instance = new Student();
                }
                return instance;
            }
        }
    }
    public void SomeMethod()
    {
    }
}

然后，您可以像这样访问学生实例： Student.Instance.SomeMethod((;