EF6种子数据填充时Tour实体GuideID与DriverID为null问题求助

我正在使用Entity Framework 6，执行种子数据填充操作时，Tour实体的GuideID和DriverID始终返回null。Tour实体关联了两个同类型的Employee实体（分别作为Guide和Driver），而且必须通过Fluent API显式设置GuideID和DriverID的索引为非唯一，否则无法正常完成数据迁移。

数据库结构中Tour表包含GuideID、DriverID外键字段，分别关联Employee表的主键。

种子数据代码 #

public static void SeedTour(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Tour>().HasData(
new Tour() { ID = 1, VehicleID = 1, Type = "Kara", Name = "Jeep Safari Turu", GuideID = 4, DriverID = 3, Price = 100, CreatedDate = DateTime.Now, Status = Entity.Enums.Status.Created, Description = "Antalya'nın doğal güzelliklerini keşfetmek için harika bir tur" },
new Tour() { ID = 2, VehicleID = 2, Type = "Köylü", Name = "Köy Turu", GuideID = 4, DriverID = 3, Price = 250, CreatedDate = DateTime.Now, Status = Entity.Enums.Status.Created, Description = "Antalya'nın doğal güzelliklerini keşfetmek için çok kötü bir tur" },
new Tour() { ID = 3, VehicleID = 3, Type = "Deniz", Name = "Yat Turu", GuideID = 4, DriverID = 3, Price = 500, CreatedDate = DateTime.Now, Status = Entity.Enums.Status.Created, Description = "Antalya'nın denzilerini keşfetmek için harika bir tur" }
    );
}

Tour实体代码 #

public class Tour : BaseEntity
{
    public string Name { get; set; }
    public string Description { get; set; }
    public string Type { get; set; }

    public int Price { get; set; }

    //Relational Properties
    public int? VehicleID { get; set; }
    public Vehicle? Vehicle { get; set; }
    public int? GuideID { get; set; }
    public Employee? Guide { get; set; }
    public int? DriverID { get; set; }

    public Employee? Driver { get; set; }
    public virtual ICollection<Ticket>? Tickets { get; set; }
}

必须的Fluent API配置（否则无法完成迁移） #

builder.Entity<Tour>()
    .HasIndex(u => u.DriverID)
    .IsUnique(false);
builder.Entity<Tour>()
    .HasIndex(u => u.GuideID)
    .IsUnique(false);

已尝试过多种注解方式，但均未解决问题，恳请帮忙。

内容的提问来源于stack exchange，提问作者Fettah Basdemir