仅填充相关对象的ID时不加载导航属性

我正在尝试建立多对一关系。表示"多"的实体具有指向父实体的导航属性。它看起来像这样：

public abstract class BaseEntity
{
    /// <summary>
    /// Key Field for all entities
    /// </summary>
    /// 
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid Id { get; set; }

    /// <summary>
    /// Date entity was created
    /// </summary>
    public DateTime DateCreated { get; set; }
    /// <summary>
    /// Last date Modified
    /// </summary>
    public DateTime DateModified { get; set; }
    /// <summary>
    /// keep track of Row Version used for concurrency
    /// </summary>
    [Timestamp]
    public Byte[] RowVersion { get; set; }
}
public abstract class Document : BaseEntity
{
    #region Primitive Properties   

    /// <summary>
    /// Boolean value to determine if Document is in an active state
    /// </summary>
    public bool IsActive { get; set; }
    /// <summary>
    /// Document comments and information
    /// </summary>
    [Required]
    public string Description { get; set; }
    #endregion
    #region Navigation Properties
    public ICollection<Comment> Comments { get; set; }
    /// <summary>
    /// FK back to User who owns document
    /// </summary>
    //public Guid OwnerId { get; set; }
    public Guid OwnerId { get; set; }
    /// <summary>
    /// Navigation Back to User who owns document
    /// </summary>
    public User Owner { get; set; }
    #endregion
}
public class Project : BaseEntity
{
    public string Name { get; set; }
    public string ProjectNumber { get; set; }
    public string Description { get; set; }
    public string CreatedBy { get; set; }
    public string ModifiedBy { get; set; }
    public string Currency { get; set; }
    #region Navigation Properties
    public virtual Address Address { get; set; }
    public virtual CompanyCode CompanyCode { get; set; }
    public virtual ICollection<Contact> TeamMembers { get; set; }
    #endregion
}    
 public class Rfi : Document
 {
    public string Number { get; set; }
    #region Navigation Properties
    //This points back to a Project Entity
    public virtual Guid ProjectId { get; set; }
    public virtual Project Project { get; set; }
    #endregion
}

因此，当我插入上述实体时，我将ProjectId从应用程序传递到Rfi实体（而不是整个Project实体）。一切都很好。我遇到的问题是，当我从数据库中取出Rfi对象时，ProjectId正在填充，但Project实体为null。默认情况下，我使用的是Lazy Loading。我是否也需要在Project实体上指定导航属性？我真的不想。除非，我可以在我的Rfi上执行映射来实现这一点。

更新：我以为EF 4.1会为我加载我的对象，但似乎有时我需要明确地包括我想要加载的对象。我不完全确定为什么。我正在使用存储库来查询我的实体。以下是我用来查询Rfi对象的方法：

    public IQueryable<TEntity> GetQuery(Expression<Func<TEntity, bool>> predicate)
    {
       return _context.Set<TEntity>().AsQueryable();
    }

我最终做了什么，在我的服务层，我这样称呼它：

public Rfi FindByNumber(string number)
{
     var rfi = rfiRepository.GetQuery(r => r.Number == number).Include(r => r.Project).Single;
     return rfi
}