关于导航属性join查询

[lostluna1]

我看到文档说只要在各实体正确配置了导航属性，则无须再手动使用LeftJoin，以下是我的导航属性配置：

[Index("idx_employee_code", nameof(EmployeeCode), true)] // 添加唯一索引
public partial class Employee : ObservableValidator
{
    [Column(IsIdentity = true, IsPrimary = true)]
    public string? EmployeeId { get; set; }

    [Column(IsNullable = false, IsIdentity = true, IsPrimary = true)]
    [DisplayName("工号")]
    [Required(ErrorMessage = "工号是必填项")]
    public string? EmployeeCode { get; set; }

    [Column(IsNullable = false)]
    [DisplayName("姓名")]
    [Required(ErrorMessage = "姓名是必填项")]
    public string? Name { get; set; }

    [DisplayName("备注")]
    public string? Remark { get; set; }

    [Column(IsNullable = false, DbType = "timestamp(6)")]
    public DateTime CreateTime { get; set; }

    [Column(IsNullable = false, DbType = "timestamp(6)")]
    public DateTime UpdateTime { get; set; }

    [Column(IsNullable = false)]
    public string DepartmentId { get; set; }

    [Navigate(nameof(DepartmentId))]
    public Department? Department { get; set; }

    [Column(IsNullable = false)]
    public string PositionId { get; set; }

    [Navigate(nameof(PositionId))]
    public Position? Position { get; set; }

    public int InActive { get; set; }
}

[Table(Name = "DEPARTMENT")]
public partial class Department : ObservableValidator
{
    [Column(IsPrimary = true)]
    //[Navigate(nameof(Employee.DepartmentId))]
    public string DepartmentId { get; set; }

    [Column(StringLength = 255, IsPrimary = true)]
    [Required(ErrorMessage = "车间名称是必填项")]
    public string DepartmentName { get; set; }

    [Column(StringLength = 255)]
    [Required(ErrorMessage = "车间代码是必填项")]
    public string DepartmentCode { get; set; }

    public List<Employee> Employees { get; set; }
}

[Table(Name = "POSITION")]
public class Position : ObservableValidator
{
    [Column(IsPrimary = true, StringLength = 255, IsNullable = false)]
    //[Navigate(nameof(Employee.PositionId))]
    public string PositionId { get; set; }

    [Column(StringLength = 255)]
    [Required(ErrorMessage = "名称不能为空")]
    public string PositionName { get; set; }

    [Column(StringLength = 255)]
    [Required(ErrorMessage = "编码不能为空")]
    public string PositionCode { get; set; }

    public List<Employee> Employees { get; set; }
}

以及代码：

var employeesMeber = new ObservableCollection<Employee>(
    await _freeSql.Select<Employee>()
                //.LeftJoin(a => a.Position.PositionId == a.PositionId)
                //.LeftJoin(a => a.Department.DepartmentId == a.DepartmentId)
                  .ToListAsync()
                  
);

这里的employeesMeber 中的Department和Position都为null，把LeftJoin取消注释就有了，和文档不符，是我的导航属性配置有问题吗，求大佬