实体模型映射LINQ

Question

我有文章和作者类。

取物品，像这样和地图实体模型：

public List<Model.Article> GetArticleList() { 
    using (var db = new ArticlesContext()) { 
     return db.Articles.Select(t => new Model.Article() { 
      Author = MapUserEntityToModel(db.Users.FirstOrDefault(u => u.UserID == t.UserID)) 
      Title = t.Title, 
      Teaser = t.Teaser 
      // etc 
     }).ToList(); 
    } 
} 

这不起作用，因为LINQ不能运行在运行时该功能。什么是最简单和最干净的方法来做映射？

这里是模型：

namespace Model { 
    public class Article { 
     public string Title { get; set; } 
     public string Teaser { get; set; } 
     public User Author { get; set; } 
     public DateTime DateAdded { get; set; } 
    } 

    public class User { 
     public string DisplayName { get; set; } 
     public string Email { get; set; } 
     public string Website { get; set; } 
     public string PasswordHash { get; set; } 
    } 
} 

这里有实体：

namespace MyProj { 
    public class Article { 
     [Key] 
     public int ArticleID { get; set; } 
     public string Title { get; set; } 
     public string Teaser { get; set; } 
     public int UserID { get; set; } 
     public DateTime DateAdded { get; set; } 
    } 

    public class User { 
     [Key] 
     public int UserID { get; set; } 
     public string DisplayName { get; set; } 
     public string Email { get; set; } 
     public string Website { get; set; } 
     public string PasswordHash { get; set; } 
    } 

    public class ArticleContext : DbContext { 
     public ArticleContext() : base("name=conn") { 
      public DbSet<Article> Articles { get; set; } 
      public DbSet<User> Users { get; set; } 
     } 
    } 
} 

Answer 1

之前继续，映射你的导航属性的关系：

public class Article { 
    [Key] 
    public int ArticleID { get; set; } 
    public string Title { get; set; } 
    public string Teaser { get; set; } 

    [ForeignKey("UserID")] 
    public virtual User Author {get; set; } // navigation property 

    public int UserID { get; set; } 
    public DateTime DateAdded { get; set; } 
} 

然后就是项目的导航属性，以他的等效模型：

public List<Model.Article> GetArticleList() { 
    using (var db = new ArticlesContext()) { 
     return db.Articles.Select(t => new Model.Article() { 
      Author = new Model.User { 
       DisplayName = t.User.DisplayName, 
       Email = t.User.Email, 
       Website = t.User.Website, 
       PasswordHash = t.User.PasswordHash 
      }, 
      Title = t.Title, 
      Teaser = t.Teaser 
      // etc 
     }).ToList(); 
    } 
} 

Answer 2

你不需要做任何事情，只是返回db.Articles直接：

using Model; 

public List<Article> GetArticleList() { 

    using(var db = new ArticlesContext()) { 
     return db.Articles.ToList(); 
    } 
} 

假设你的EF模型使用外键正确设置，您的Article类型将进行懒惰评估Author属性在访问时将返回User对象。