EF Core 6 无法确定导航表示的关系

Question

我的 DbContext 中有以下表：

    public class Employee 
    {
        [Key]
        public int Id { get; set; }
        public long EmployeeCode { get; set; }
        public UserRole Role { get; set; }
        public string? Salutation { get; set; }
        public string? FirstName { get;set; }
        public string? MiddleName { get;set; }
        public string? LastName { get;set; }
        public string? DisplayName { get; set; }  
        public virtual Address? Address { get; set; }
        public byte[]? Image { get; set; } = null;
        public DateTime Created { get; set; }
        public UserStatus Status { get; set; }
        public virtual Institution? Institution { get; set; }
        public virtual List<Permission>? Permissions { get; set; }        
        public virtual List<EmploymentLog> EmploymentLogs { get; set; }
        public bool HasAllPermission()
        {
            return HasPermission(Tasks.All);
        }

        public bool HasPermission(Tasks task)
        {
            //If no permissions were granted, return false
            if (Permissions == null) return false;

            //Check if user has all permission
            if (Permissions.FirstOrDefault(p => p.Task == Tasks.All && p.Access) != null) return true;

            //Check for the specific permisson           
            var permission = Permissions.FirstOrDefault(p => p.Task == task);
            return permission != null && permission.Access;
        }

   public bool HasPermissionSuper(Tasks task)
        {
            //If no permissions were granted, return false
            if (Permissions == null) return false;

            //Check if user has all permission
            if (Permissions.FirstOrDefault(p => p.Task == Tasks.Super && p.Access) != null) return true;

            //Check for the specific permisson           
            var permission = Permissions.FirstOrDefault(p => p.Task == task);
            return permission != null && permission.Access;
        }
    }
    public class EmploymentLog
    {
        [Key]
        public int Id { get; set; }
        public virtual Employee Employee { get; set; }
        public EmploymentEventType EventType { get; set; }
        public virtual Employee InitiatedBy { get; set; }
        public DateTime InitiatedOn { get; set; }
        public EmploymentEventStatus Status { get; set; }
        public virtual Employee ApprovedBy { get; set; }
        public virtual DateTime ApprovedOn { get; set; }
    }

    //Model Builder:
    modelBuilder.Entity<EmploymentLog>()
              .HasOne(e => e.Employee)
              .WithMany(e => e.EmploymentLogs)
              .OnDelete(DeleteBehavior.NoAction);

员工表保存了所有员工的记录，EmploymentLogs表保存了员工的雇佣记录的变化记录，例如员工第一次加入公司时，EmploymentLogs表中生成的记录，或者当员工被解雇时。员工晋升、降职、暂停或终止时，EmploymentLogs 表中会生成一条记录，在更新数据库时出现以下错误：

无法确定“Employee”类型的导航“EmploymentLog.ApprovedBy”表示的关系。手动配置关系，或者使用“[NotMapped]”属性或使用“OnModelCreating”中的“EntityTypeBuilder.Ignore”忽略此属性。

我以前使用过 EF6，这样的代码可以很好地运行，我做错了什么？

Answer 1

我以前使用过 EF6，这样的代码可以很好地运行，我做错了什么？

忘记 EF6。尽管存在一些相似之处，但 EF Core 是完全不同的系统，具有您需要遵循的自己的约定和规则。

该错误消息表明 EF Core 无法自动确定某些关系。当您对另一个实体具有多个导航属性时，通常会发生这种情况，并且在您的情况下，该实体具有 3 个到- 、和的EmploymentLog引用导航，而另一个实体具有到-的单个集合导航属性。EmployeeEmployeeInitiatedByApprovedByEmployeeeEmploymentLogEmploymentLogs

因此，您至少需要显式映射关联关系（导航属性对、外键、级联删除行为等）。您已经对其中一个进行了操作，现在对另外两个进行相同的操作，例如

// EmploymentLog relationships

// Employee (many-to-one)
modelBuilder.Entity<EmploymentLog>()
    .HasOne(e => e.Employee) // reference
    .WithMany(e => e.EmploymentLogs) // collection
    .OnDelete(DeleteBehavior.NoAction);

// InitiatedBy (many-to-one)
modelBuilder.Entity<EmploymentLog>()
    .HasOne(e => e.InitiatedBy) // reference
    .WithMany() // no collection
    .OnDelete(DeleteBehavior.NoAction);

// ApprovedBy (many-to-one)
modelBuilder.Entity<EmploymentLog>()
    .HasOne(e => e.ApprovedBy) // reference
    .WithMany() // no collection
    .OnDelete(DeleteBehavior.NoAction);