實體模型映射LINQ

Question

我有文章和作者類。

取物品，像這樣和地圖實體模型：

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(); 
    } 
} 

這不起作用，因爲LINQ不能運行在運行時該功能。什麼是最簡單和最乾淨的方法來做映射？

這裏是模型：

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; } 
    } 
} 

這裏有實體：

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

之前繼續，映射你的導航屬性的關係：

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; } 
} 

然後就是項目的導航屬性，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(); 
    } 
} 

假設你的EF模型使用外鍵正確設置，您的Article類型將進行懶惰評估Author屬性在訪問時將返回User對象。