我有 4 个类和类属性，但我应该如何关联这些类？（一对一，一对多……）答案

【问题标题】：I have 4 class and class properties, but how should I relate the classes? (one-one, one-many ...)我有 4 个类和类属性，但我应该如何关联这些类？（一对一，一对多……）
【发布时间】：2020-07-16 15:32:46
【问题描述】：

哪个表应该与哪个表关联？

如何添加外键？

我很困惑。你能帮帮我吗？

ex : 用户和部门 ---> 一对多？

  public class User
    {
        public int UserId { get; set; } 
        public string Username { get; set; } 
        public string Email { get; set; } 
        public string Password { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int DepartmentId { get; set; }
        public int TitleId { get; set; }
        public int ManagerUserId { get; set; }
    }
    public class Department
    {
        public int DepartmentId { get; set; }
        public string DepartmentCode { get; set; }
        public string Name { get; set; }
        public int ManagerDepartmentId { get; set; }
        public int ManagerUserId { get; set; }
    }
    public class Position
    {
        public int PositionId { get; set; }
        public string PositionCode { get; set; }
        public string Name { get; set; }
        public int UserId { get; set; }
        public byte Status { get; set; }
    }
    public class Title
    {
        public int TitleId { get; set; }
        public string Name { get; set; }
        public byte IsIntegrationData { get; set; }
    }

【问题讨论】：

标签： c# sql entity-framework

【解决方案1】：

用户和部门是一对多的关系。我建议你看这里： An example how configure One-to-Many relationship between two entities in Entity Framework 6 using the code-first approach.

【讨论】：

【解决方案2】：

试试这样的：

  public class User
    {
        public int UserId { get; set; } 
        public string Username { get; set; } 
        public string Email { get; set; } 
        public string Password { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }

        [ForeignKey("Department")]
        public int DepartmentId { get; set; }
        public virtual Department Department {get; set;}
        
        [ForeignKey("Title")]
        public int TitleId { get; set; }
        public virtual Title Title {get;set;}

        [ForeignKey("Manager")]
        public int ManagerUserId { get; set; }
        public virtual User Manager {get; set;}
        
        [InverseProperty("Manager")]
        public virtual List<Department> DepartmentsManaged {get; set;}
    }


    public class Department
    {
        public int DepartmentId { get; set; }
        public string DepartmentCode { get; set; }
        public string Name { get; set; }

        [ForeignKey("Manager")]
        public int ManagerUserId { get; set; }
        public virtual User Manager {get; set;}

        public virtual List<User> Users {get; set;}
    }


    public class Position
    {
        public int PositionId { get; set; }
        public string PositionCode { get; set; }
        public string Name { get; set; }

        [Required]
        [ForeignKey("User")]
        public int UserId { get; set; }
        public virtual User User {get; set;}

        public byte Status { get; set; }
    }
    public class Title
    {
        public int TitleId { get; set; }
        public string Name { get; set; }
        public byte IsIntegrationData { get; set; }

        public virtual List<User> Users {get; set;}
    }

我删除了一些字段，例如 ManagerDepartmentId，因为这应该通过导航属性 Department.Manager.DepartmentId 访问。

【讨论】：