如何读取 EF 5 中的 NotMapped 属性？

Question

我不知道如何访问标记为 NotMapped 的属性，因此我可以打印它。当我尝试访问它时，我得到了

LINQ to Entities 不支持指定的类型成员“LinkAddress”。仅支持初始化器、实体成员和实体导航属性。

我的 LINQ 查询是：

(from n in db.Navigation
                                  join s in db.Sections on n.SectionID equals s.SectionID
                                  join sl in db.Locale_Sections on s.SectionID equals sl.SectionID
                                  where n.Category == "Books" && sl.CultureID == 1
                                  select new
                                  {
                                      s.LinkAddress,
                                      sl.Title,
                                  }).ToList();

我的部分上下文是：

    [Table("Section")]
public class Section
{
    [Key, Required, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Int16 SectionID { get; set; }

    public Int64 LogoFileID { get; set; }

    [ForeignKey("LogoFileID")]
    public virtual File File { get; set; }

    [Required, MaxLength(15), Column(TypeName = "varchar")]
    public string RouteName { get; set; }

    [Required, MaxLength(15), Column(TypeName = "varchar")]
    public string Type { get; set; }

    public virtual ICollection<Locale_Section> Translations { get; set; }

    [NotMapped]
    public string LinkAddress
    {
        get
        {
            return Type + "/" + RouteName;
        }
    }
}

Answer 1

由于它没有被映射，它不能在查询中使用……你必须先实现对象，然后才能访问属性……

var materialised = (from n in db.Navigation
     join s in db.Sections on n.SectionID equals s.SectionID
     join sl in db.Locale_Sections on s.SectionID equals sl.SectionID
     where n.Category == "Books" && sl.CultureID == 1
     select new
     {
          s,
          sl.Title,
     }).ToList()

// This bit is done in CLR
return materialised.Select(m => new 
{
    m.s.LinkAddress,
    m.Title
});

或者，您可以将您的逻辑带入有效的查询中......

(from n in db.Navigation
 join s in db.Sections on n.SectionID equals s.SectionID
 join sl in db.Locale_Sections on s.SectionID equals sl.SectionID
 where n.Category == "Books" && sl.CultureID == 1
 select new
 {
     LinkAddress = s.Type + "/" + s.RouteName,
     sl.Title,
 }).ToList()