Entity Framework 4.x: POCOs入门

        POCOs 是在Visual Studio 2010和ASP.NET 4.0中开始支持的一个新特性，其入门十分简单，下面我们基于Entity Framework 4.0.来实现一个基于POCOs的代码示例。

        首先，创建一个测试工程

        然后，新建一个Ado.NET Entity Data Model文件

       如下图所示，定义两个类：Albums 和Photos

      接下来我们还要确认是否已经关闭了代码自动生成，在Solution Explorer 选择edmx定义文件，在属性框确认Custom Tool为空，如下图所示：

定义以上两个对象的结构

1. public class Albums
2.     {
3.         public Int32 Id { get; set; }
4.         public String AlbumName { get; set; }
5.         public String Remark { get; set; }
6.         public IList<Photos> Photos { get; set; }
7.     }

1. public class Photos
2.     {
3.         public Int32 Id { get; set; }
4.         public String Name { get; set; }
5.         public String Description { get; set; }
6.         public String PicPath { get; set; }
7.         public Int32 Album_Id { get; set; }
8.         public Albums Albums { get; set; }
9.     }

然后建立自己的继承于ObjectContext的对象,在该对象中我们将定义需要使用LINQ查询的对象集合。如下所示：

1. public class Mvc3SampleModel : ObjectContext
2.     {
3.         private readonly ObjectSet<Albums> _albums;
4.         private readonly ObjectSet<Photos> _photos;
5.  
6.         public Mvc3SampleModel()
7.             : base("Name=DbEntities", "DbEntities")
8.         {
9.             ContextOptions.LazyLoadingEnabled = true;
10.             _albums = CreateObjectSet<Albums>("Albums");
11.             _photos = CreateObjectSet<Photos>("Photos");
12.         }
13.  
14.         public ObjectSet<Albums> Albums
15.         {
16.             get { return _albums; }
17.         }
18.  
19.         public ObjectSet<Photos> Photos
20.         {
21.             get { return _photos; }
22.         }

下面演示基于LINQ进行查询的一般情况：

1. public void GalleryTest()
2.       {
3.           var context = new Mvc3SampleModel();
4.           var visibleAlbums = from a in context.Albums
5.                               where a.AlbumName !=null
6.                               select a;
7.           foreach (var visibleAlbum in visibleAlbums)
8.           {
9.               Console.WriteLine(visibleAlbum.AlbumName);
10.           }
11.           var searchPhotos = from p in context.Photos
12.                              where p.Name.StartsWith("M")
13.                              select p;
14.           foreach (var searchPhoto in searchPhotos)
15.           {
16.               Console.WriteLine(searchPhoto.Name);
17.           }
18.       }

    以下为测试结果