急于在通用存储库模式中加载多个级别的导航属性的问题

Question

我最近开始在新应用程序中使用通用存储库模式，我一直遵循Chris Pratt Truly Generic Repository的指南。我急切地将导航属性加载到这样的GetQueryable方法中

if (includeProperties != null)
        {
            foreach (var includeProperty in includeProperties.Split
                (new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
            {
                query = query.Include(includeProperty);
            }
        }
else
        {
            foreach (var property in context.Model.FindEntityType(typeof(TEntity)).GetNavigations())
                query = query.Include(property.Name);
        }

现在，第一级导航属性可以很好地加载，但是如果我在导航属性中具有导航属性，即第二级没有被加载，则返回null，

public partial class Project : Entity<int>
{
    public Project()
    {
        this.UserProjects = new HashSet<UserProject>();
    }
    [Required]
    public string Title { get; set; }
    public virtual ICollection<UserProject> UserProjects { get; set; }  
}

public class UserProject : Entity<int>
{
    public int UserId { get; set; }
    public virtual User User { get; set; }
    public int ProjectId { get; set; }
    public virtual Project Project { get; set; }
}

public class User : IdentityUser<int>
{
    public User()
    {
        this.UserProjects = new HashSet<UserProject>();
    }  
    public Photo Photo { get; set; }
    public virtual ICollection<UserProject> UserProjects { get; set; }             
}

在这里，当我查询项目时，正确填充了UserProject，并且在UpserProjects内部也填充了Project，但是尽管UserProject具有userId，但User为null。