MVC Music Sotre 2

七、使用EF快速完成CRUD功能

(1)新建Artist,Genre,Album3个类,用属性显示3张表的关联

(2)添加DbContext类(对应数据库),添加DbSet<Model>(对应表) 

 >画出数据库设计图(表、表间关系),手动、UML、SQL的工具均可

  

>添加Album、Genre、Artist类,和DbContext类

    public class DbMusicContext:DbContext //相当于数据库
    {
        public DbSet<Album> Albums { get; set; }  //Album表
        public DbSet<Genre> Genres { get; set; }  //Genre表
    }

八、创建DCDIMC派生类,Database.SetInitializer（DCDIMC派生） 创建数据库并录入记录（DCDIMC的功能）

         备注：>SampleData类必须继承DropCreateDatabaseIfModelChanges<T> 类,T是DbContext派生类(在此是DbMusicContext)

                 >DCDIMC类用于将已有数据添加到sdf中.若只关注数据的CRUD操作,八、九可以跳过.

                 (1)Webconfig中连接DbContext类。DataSource和provider Name

                       

  <connectionStrings>
    <!--EF模式下,连接name属性写DbContext类的名称-->
    <add name ="DbContextMusic" connectionString ="Data Source=|DataDirectory|MusicDb.sdf" providerName ="System.Data.SqlServerCe.4.0"/>
  </connectionStrings>

(2)添加DCDIMC 派生类，并override seed方法

       

namespace Music.Models
{
    public class SampleData : DropCreateDatabaseIfModelChanges<DbContextMusic>
    {
        protected override void Seed(DbContextMusic context)
        {
            var genres = new List<Genre>
            {
                new Genre { Name = "Rock" },
                new Genre { Name = "Jazz" },
                new Genre { Name = "Metal" },
                new Genre { Name = "Alternative" },
                new Genre { Name = "Disco" },
                new Genre { Name = "Blues" },
                new Genre { Name = "Latin" },
                new Genre { Name = "Reggae" },
                new Genre { Name = "Pop" },
                new Genre { Name = "Classical" }
            };

            var artists = new List<Artist>

 (3)在Global.asax中 Database.SetInitilizer( new DCDIMC派生类)

        protected void Application_Start()
        {
            Database.SetInitializer(new SampleData());
            //SetInitializer的参数是  DCDIMC派生类
            //new 数据库初始类名

运行效果：

创建了数据库MusicDb.sdf，并且添加了3张表。 在DCDIMC中声明的记录都已录入对应表.(记住,在DbContext中只声明了DbSet<Album>和DbSet<Genre>)

 九、DCDIMC录入数据疑问

DCDIMC的Seed写法（1）：

 var genres = new List<Genre>
            {
                new Genre { Name = "Rock" },
                 ....
new Genre { Name = "Classical" }
            };

            var artists = new List<Artist>
            {
                new Artist { Name = "Aaron Copland & London Symphony Orchestra" },
    .........................
                new Artist { Name = "Zeca Pagodinho" }
            };

            var albums = new List<Album>
            {
                new Album { Title = "The Best Of Men At Work", Genre = genres.Single(g => g.Name == "Rock"), Price = 8.99M, Artist = artists.Single(a => a.Name == "Men At Work"), AlbumArtUrl = "/Content/Images/placeholder.gif" },
               ....
                new Album { Title = "Ao Vivo [IMPORT]", Genre = genres.Single(g => g.Name == "Latin"), Price = 8.99M, Artist = artists.Single(a => a.Name == "Zeca Pagodinho"), AlbumArtUrl = "/Content/Images/placeholder.gif" }
            };

//执行后Album表、Genre表、Artist表都无任何记录

Seed写法2：

 var genres = new List<Genre>
            {
                new Genre { Name = "Rock" },
                 ....
new Genre { Name = "Classical" }
            };

            var artists = new List<Artist>
            {
                new Artist { Name = "Aaron Copland & London Symphony Orchestra" },
    .........................
                new Artist { Name = "Zeca Pagodinho" }
            };

            new List<Album>
            {
                new Album { Title = "The Best Of Men At Work", Genre = genres.Single(g => g.Name == "Rock"), Price = 8.99M, Artist = artists.Single(a => a.Name == "Men At Work"), AlbumArtUrl = "/Content/Images/placeholder.gif" },
               ....
                new Album { Title = "Ao Vivo [IMPORT]", Genre = genres.Single(g => g.Name == "Latin"), Price = 8.99M, Artist = artists.Single(a => a.Name == "Zeca Pagodinho"), AlbumArtUrl = "/Content/Images/placeholder.gif" }
            }.ForEach(a => context.Albums.Add(a));

//尽管只有context.Albums.add(a) ,记录都已经录入3个表.

 十、实现Album的CRUD操作

     (1)添加AlbumController

     (2)向导中选择Model和DbContext  //效果实现

     (3)记忆Controller和Views中生成的代码

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