EF Core 5，如何定义多个 "one-many" 关系？

Question

我正在创建一个自由任务管理应用程序。这是逻辑。这些是涉及的 3 个 POCO

用户（登录用户）

A user can create any number of clients

A user can create any number of projects

A user is created, updated by another user

客户（自由客户）

A client can have any number of projects

A client is created, updated by a user

项目

A project should have only one client

A project is created, updated by a user

这些是我的实体。我正在使用 Code-First 方法并使用 SQLServer。我删除了许多属性以便在此处发布

用户实体

public class User
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Key]
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }        

    public DateTime? CreatedOn { get; set; }
    public DateTime? UpdatedOn { get; set; }
    public virtual User CreatedBy { get; set; }
    public virtual User UpdatedBy { get; set; }

    [ForeignKey("UserId")]
    public int? CreatedById { get; set; }
    [ForeignKey("UserId")]
    public int? UpdatedById { get; set; }

    public virtual ICollection<Project> Projects { get; set; }
    public virtual ICollection<Client> Clients { get; set; }        
}

客户端实体

public class Client
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Key]
    public int Id { get; set; }
    public string Company { get; set; }
    public string Email { get; set; }
    public string Phone { get; set; }
    public string Address { get; set; }        

    public DateTime? CreatedOn { get; set; }
    public DateTime? UpdatedOn { get; set; }
    public virtual User CreatedBy { get; set; }
    public virtual User UpdatedBy { get; set; }

    [ForeignKey("UserId")]
    public int? CreatedById { get; set; }
    [ForeignKey("UserId")]
    public int? UpdatedById { get; set; }

    public ICollection<Project> Projects { get; set; }
}

项目实体

public class Project
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public string ProjectLogo { get; set; }        

    public DateTime? CreatedOn { get; set; }
    public DateTime? UpdatedOn { get; set; }
    public virtual User CreatedBy { get; set; }
    public virtual User UpdatedBy { get; set; }

    [ForeignKey("UserId")]
    public int? CreatedById { get; set; }
    [ForeignKey("UserId")]
    public int? UpdatedById { get; set; }

    public virtual Client Client { get; set; }       
}

我现在面临着很多关于 ForginKeys 和映射的问题。这里的实体映射有什么问题？我无法在具有相同 CreatedById 的客户端 table 中插入 2 行，EF 正在使用唯一值对其进行约束。

这是我的流利映射

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        //User
        modelBuilder.Entity<User>().HasOne(a => a.CreatedBy).WithOne().OnDelete(DeleteBehavior.NoAction);
        modelBuilder.Entity<User>().HasOne(a => a.UpdatedBy).WithOne().OnDelete(DeleteBehavior.NoAction);
        //Project
        modelBuilder.Entity<Project>().HasOne(a => a.CreatedBy).WithOne().OnDelete(DeleteBehavior.NoAction);
        modelBuilder.Entity<Project>().HasOne(a => a.UpdatedBy).WithOne().OnDelete(DeleteBehavior.NoAction);
        //Client
        modelBuilder.Entity<Client>().HasOne(a => a.CreatedBy).WithOne().OnDelete(DeleteBehavior.NoAction);
        modelBuilder.Entity<Client>().HasOne(a => a.UpdatedBy).WithOne().OnDelete(DeleteBehavior.NoAction);
    }

我怎样才能实现这个要求？

Answer 1

这是与我的实体的关系问题。我让我的属性看起来像

public DateTime? CreatedOn { get; set; }
public DateTime? UpdatedOn { get; set; }
public virtual User CreatedBy { get; set; }
public virtual User UpdatedBy { get; set; }
public int? CreatedById { get; set; }
public int? UpdatedById { get; set; }

并添加了流畅的映射

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            //User
            modelBuilder.Entity<User>().HasOne(a => a.CreatedBy).WithMany().OnDelete(DeleteBehavior.SetNull);
            modelBuilder.Entity<User>().HasOne(a => a.UpdatedBy).WithMany().OnDelete(DeleteBehavior.SetNull);
            //Project
            modelBuilder.Entity<Project>().HasOne(a => a.CreatedBy).WithMany().OnDelete(DeleteBehavior.SetNull);
            modelBuilder.Entity<Project>().HasOne(a => a.UpdatedBy).WithMany().OnDelete(DeleteBehavior.SetNull);
            //Client
            modelBuilder.Entity<Client>().HasOne(a => a.CreatedBy).WithMany().OnDelete(DeleteBehavior.SetNull);
            modelBuilder.Entity<Client>().HasOne(a => a.UpdatedBy).WithMany().OnDelete(DeleteBehavior.SetNull);
        }

添加一对多关系解决了我的问题。感谢@David

EF Core 5，如何定义多个 "one-many" 关系？

EF Core 5, How to define multiple "one-many" relationships?

c#

sql-server

entity-framework

ef-core-5.0

用户（登录用户）

客户（自由客户）

项目

用户实体

客户端实体

项目实体