在EF5 Code First中检索一对零/一对多数据

Question

使用EF5 Code First我有以下两个类：

public class MicroPost : IEntity
{
    private ICollection<Hashtag> hashtags;
    private ICollection<MicroPostComment> comment;
    private ICollection<FlaggedInappropriate> flag;

    public long Id { get; set; }

    public int SenderId { get; set; }

    public int CreatorId { get; set; }

    public string Body { get; set; }

    public virtual ICollection<Hashtag> Hashtags
    {
        get { return hashtags ?? new HashSet<Hashtag>(); }
        set { hashtags = value; }
    }

    public virtual ICollection<MicroPostComment> Comments
    {
        get { return comment ?? new HashSet<MicroPostComment>(); }
        set { comment = value; }
    }

    public int Like { get; set; }

    public bool FlagInappropriate
    {
        get { return FlagInappropriates.Any(x => x.Approved); }
    }

    public ICollection<FlaggedInappropriate> FlagInappropriates
    {
        get { return flag ?? new HashSet<FlaggedInappropriate>(); }
        set { flag = value; }
    }

    public DateTime DateSent { get; set; }
}


public class MicroPostComment : IEntity
{
    private ICollection<FlaggedInappropriate> flag;

    public long Id { get; set; }

    public long? MicropostId { get; set; }

    public int SenderId { get; set; }

    public string Body { get; set; }

    public bool FlagInappropriate
    {
        get { return FlagInappropriates.Any(x => x.Approved); }
    }

    public ICollection<FlaggedInappropriate> FlagInappropriates
    {
        get { return flag ?? new HashSet<FlaggedInappropriate>(); }
        set { flag = value; }
    }

    public DateTime DateSent { get; set; }
}

两个类之间的关系按以下方式配置：

public class MicroPostConfig : EntityTypeConfiguration<MicroPost>, IEntityConfiguration
{
    public MicroPostConfig()
    {
        HasKey(p => p.Id);
        Property(p => p.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity).HasColumnName("ID");
        Property(p => p.Body).HasColumnType("nvarchar").HasMaxLength(50).IsRequired().HasColumnName("BODY");
        Property(p => p.SenderId).IsRequired().HasColumnName("SENDER_ID");
        Property(p => p.CreatorId).IsRequired().HasColumnName("CREATOR_ID");
        Property(p => p.Like).IsRequired().HasColumnName("LIKE");
        Property(p => p.DateSent).IsRequired().HasColumnName("DATE_SENT");

        Ignore(p => p.FlagInappropriate);

        // Navigation properties

        HasMany(r => r.Hashtags).WithOptional().HasForeignKey(n => n.MicropostId);
        HasMany(r => r.Comments).WithOptional().HasForeignKey(n => n.MicropostId);
        HasMany(r => r.FlagInappropriates).WithOptional().HasForeignKey(n => n.PostId).WillCascadeOnDelete(false);
    }

    /// <summary>
    /// Adds the configuration.
    /// </summary>
    /// <param name="registrar">The registrar.</param>
    public void AddConfiguration(ConfigurationRegistrar registrar)
    {
        registrar.Add(this);
    }
}

以下方法通过急切加载评论来检索帖子：

public IEnumerable<MicroPost> GetPostsWithComments(DateTime? fromDate = null, DateTime? toDate = null,int fromIndex = 0, int maxMessages = 20)
{
    if (toDate == null)
        toDate = DateTime.Now;

    IEnumerable<MicroPost> result = fromDate != null
                                        ? repository.GetQuery(x => x.DateSent >= fromDate.Value && x.DateSent <= toDate).Include(x => x.Comments)
                                        : repository.GetQuery(x => x.DateSent <= toDate).Include(x => x.Comments);

    return result.AsEnumerable();
}

EF5生成以下SQL：

SELECT 
[Project1].[SENDER_ID] AS [SENDER_ID], 
[Project1].[ID] AS [ID], 
[Project1].[CREATOR_ID] AS [CREATOR_ID], 
[Project1].[BODY] AS [BODY], 
[Project1].[LIKE] AS [LIKE], 
[Project1].[DATE_SENT] AS [DATE_SENT], 
[Project1].[C1] AS [C1], 
[Project1].[ID1] AS [ID1], 
[Project1].[MICROPOST_ID] AS [MICROPOST_ID], 
[Project1].[SENDER_ID1] AS [SENDER_ID1], 
[Project1].[BODY1] AS [BODY1], 
[Project1].[DATE_SENT1] AS [DATE_SENT1]
FROM ( SELECT 
    [Extent1].[ID] AS [ID], 
    [Extent1].[SENDER_ID] AS [SENDER_ID], 
    [Extent1].[CREATOR_ID] AS [CREATOR_ID], 
    [Extent1].[BODY] AS [BODY], 
    [Extent1].[LIKE] AS [LIKE], 
    [Extent1].[DATE_SENT] AS [DATE_SENT], 
    [Extent2].[ID] AS [ID1], 
    [Extent2].[MICROPOST_ID] AS [MICROPOST_ID], 
    [Extent2].[SENDER_ID] AS [SENDER_ID1], 
    [Extent2].[BODY] AS [BODY1], 
    [Extent2].[DATE_SENT] AS [DATE_SENT1], 
    CASE WHEN ([Extent2].[SENDER_ID] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
    FROM  [dbo].[MicroPost] AS [Extent1]
    LEFT OUTER JOIN [dbo].[MicroPostComment] AS [Extent2] ON [Extent1].[ID] = [Extent2].[MICROPOST_ID]
    WHERE  CAST( [Extent1].[DATE_SENT] AS datetime2) <= @p__linq__0
)  AS [Project1]
ORDER BY [Project1].[ID] ASC, [Project1].[C1] ASC

如果我在db上运行此查询，则会检索包含注释的数据。但是，MicroPost类的属性Comments始终为null。任何人都知道可能出错的地方。我们已经尝试了所有类型的配置选项而没有结果，我们很难理解为什么这不起作用。