学习EF之CodeFirst二（数据库对应映射）

一：Data Annotations 此方法是利用在实体的那个属性里增加特性来进行操作控制；这些特性是在using System.ComponentModel.DataAnnotations下，要引用DLL using System.ComponentModel.DataAnnotations; namespace ModelLib{ public class Car { [Key] publi

一：Data Annotations

此方法是利用在实体的那个属性里增加特性来进行操作控制；这些特性是在using System.ComponentModel.DataAnnotations下，要引用DLL

<span>using</span><span> System.ComponentModel.DataAnnotations;
</span><span>namespace</span><span> ModelLib
{
    </span><span>public</span> <span>class</span><span> Car
    {
        [Key]
        </span><span>public</span> <span>int</span> ID { <span>get</span>; <span>set</span><span>; }

        [Required(ErrorMessage</span>=<span>"</span><span>不能为空</span><span>"</span><span>)]
        </span><span>public</span> <span>string</span> CarNum { <span>get</span>; <span>set</span><span>; }

        [StringLength(</span><span>10</span>,ErrorMessage=<span>"</span><span>最大长度不能超过10个字符</span><span>"</span><span>)]
        </span><span>public</span> <span>string</span> Colour { <span>get</span>; <span>set</span><span>; }

        [Range(</span><span>1</span>,<span>10</span>,ErrorMessage=<span>"</span><span>UserYear取证范围在1-10之间</span><span>"</span><span>)]
        </span><span>public</span> <span>int</span> UserYear { <span>get</span>; <span>set</span><span>; }

        [RegularExpression(</span><span>@"</span><span>^[\w-]+(\.[\w-]+)*@[\w-]+(\.[\w-]+)+$</span><span>"</span><span>)]
        </span><span>public</span> <span>string</span> Email { <span>get</span>; <span>set</span><span>; }
    }
}</span>

假如我们代码没有按照上面规定来便会报出异常：

上面只是列出一部分的特性，其它特性可以查MSDN：http://msdn.microsoft.com/zh-cn/library/system.componentmodel.dataannotations.aspx

 

二：Fluent API（推荐使用，因为前一种范围有限）

1：我们可以在EF上下文里重写OnModelCreating然后对要设置的属性进行操作，但是这样一个实体类如果有3个属性需要配置，10个实体类就需要配置30个，那么就得在OnModelCreating方法里写30行，很麻烦且不易维护,所以一般不这么编写；

<span>using</span><span> System.Data.Entity;
</span><span>using</span><span> ModelLib;
</span><span>namespace</span><span> DataLibrary
{
    </span><span>public</span> <span>class</span><span> MyDbContext : DbContext
    {
        </span><span>public</span><span> MyDbContext()
            : </span><span>base</span>(<span>"</span><span>name=MyTestDb</span><span>"</span><span>)
        {
        }

        </span><span>protected</span> <span>override</span> <span>void</span><span> OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity</span><home>().HasKey(d =><span> d.ID);
            modelBuilder.Entity</span><home>().Property(d =><span> d.Address).IsRequired();
            modelBuilder.Entity</span><person>().Property(p => p.PassWord).HasMaxLength(<span>50</span><span>);
        }


        </span><span>public</span> DbSet<person> Person { <span>get</span>; <span>set</span><span>; }

        </span><span>public</span> DbSet<home> Home { <span>get</span>; <span>set</span><span>; }

        </span><span>public</span> DbSet<car> Car { <span>get</span>; <span>set</span><span>; }
    }
}</span></car></home></person></person></home></home>

2：注意返回值可以看出modelBuilder的Entity泛型方法的返回值是EntityTypeConfiguration泛型类。我们可以定义一个继承自EntityTypeConfiguration泛型类的类来定义domain中每个类的数据库配置。
ok，我们在DataAccess类库下新建一个继承自EntityTypeConfiguration泛型类的DestinationMap类，在构造函数里写上配置：

<span>using</span><span> System.Data.Entity.ModelConfiguration;
</span><span>using</span><span> System.Linq;
</span><span>using</span><span> System.Text;
</span><span>using</span><span> ModelLib;
</span><span>namespace</span><span> DataLibrary
{
    </span><span>public</span> <span>class</span> HomeMap:EntityTypeConfiguration<home><span>
    {
        </span><span>public</span><span> HomeMap()
        {
            Property(d </span>=><span> d.Address).IsRequired();
        }
    }
}</span></home>

<span>using</span><span> System.Data.Entity.ModelConfiguration;
</span><span>using</span><span> System.Linq;
</span><span>using</span><span> System.Text;
</span><span>using</span><span> ModelLib;

</span><span>namespace</span><span> DataLibrary
{
    </span><span>public</span> <span>class</span> PersonMap:EntityTypeConfiguration<person><span>
    {
        </span><span>public</span><span> PersonMap()
        {
            Property(d </span>=><span> d.Age).IsRequired();
        }
    }
}</span></person>

然后修改EF上下文：

<span>using</span><span> System.Data.Entity;
</span><span>using</span><span> ModelLib;
</span><span>namespace</span><span> DataLibrary
{
    </span><span>public</span> <span>class</span><span> MyDbContext : DbContext
    {
        </span><span>public</span><span> MyDbContext()
            : </span><span>base</span>(<span>"</span><span>name=MyTestDb</span><span>"</span><span>)
        {
        }


        </span><span>protected</span> <span>override</span> <span>void</span><span> OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(</span><span>new</span><span> HomeMap());
            modelBuilder.Configurations.Add(</span><span>new</span><span> PersonMap());
        }

        </span><span>public</span> DbSet<person> Person { <span>get</span>; <span>set</span><span>; }

        </span><span>public</span> DbSet<home> Home { <span>get</span>; <span>set</span><span>; }

        </span><span>public</span> DbSet<car> Car { <span>get</span>; <span>set</span><span>; }
    }
}</span></car></home></person>

下面是一些常用的设置：

<span>//</span><span>【主键】
</span><span>//</span><span>Data Annotations：</span>
<span>[Key]
</span><span>public</span> <span>int</span> DestinationId { <span>get</span>; <span>set</span><span>; }

</span><span>//</span><span>Fluent API：</span>
<span>public</span> <span>class</span><span> BreakAwayContext : DbContext
{
    </span><span>protected</span> <span>override</span> <span>void</span><span> OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity</span><destination>().HasKey(d =><span> d.DestinationId);
    }
}

</span><span>//</span><span>【外键】
</span><span>//</span><span>Data Annotations：</span>
<span>public</span> <span>int</span> DestinationId { <span>get</span>; <span>set</span><span>; }
[ForeignKey(</span><span>"</span><span>DestinationId</span><span>"</span><span>)]
</span><span>public</span> Destination Destination { <span>get</span>; <span>set</span><span>; }

</span><span>//</span><span>Fluent API：</span>
modelBuilder.Entity<lodging>().HasRequired(p => p.Destination).WithMany(p=>p.Lodgings).HasForeignKey(p =><span> p.DestinationId);

</span><span>//</span><span>【长度】
</span><span>//</span><span>Data Annotations：通过StringLength(长度),MinLength(最小长度),MaxLength(最大长度)来设置数据库中字段的长度</span>
[MinLength(<span>10</span>),MaxLength(<span>30</span><span>)]
</span><span>public</span> <span>string</span> Name { <span>get</span>; <span>set</span><span>; }
[StringLength(</span><span>30</span><span>)]
</span><span>public</span> <span>string</span> Country { <span>get</span>; <span>set</span><span>; }

</span><span>//</span><span>Fluent API：没有设置最小长度这个方法</span>
modelBuilder.Entity<destination>().Property(p => p.Name).HasMaxLength(<span>30</span><span>);
modelBuilder.Entity</span><destination>().Property(p => p.Country).HasMaxLength(<span>30</span><span>);

</span><span>//</span><span>【非空】
</span><span>//</span><span>Data Annotations：</span>
[Required(ErrorMessage=<span>"</span><span>请输入描述</span><span>"</span><span>)]
</span><span>public</span> <span>string</span> Description { <span>get</span>; <span>set</span><span>; }

</span><span>//</span><span>Fluent API:</span>
modelBuilder.Entity<destination>().Property(p =><span> p.Country).IsRequired();

</span><span>//</span><span>【数据类型】</span>
<span>Data Annotations：
将string映射成ntext，默认为nvarchar(max)
[Column(TypeName </span>= <span>"</span><span>ntext</span><span>"</span><span>)]
</span><span>public</span> <span>string</span> Owner { <span>get</span>; <span>set</span><span>; }

</span><span>//</span><span>Fluent API:</span>
modelBuilder.Entity<lodging>().Property(p => p.Owner).HasColumnType(<span>"</span><span>ntext</span><span>"</span><span>);

</span><span>//</span><span>【表名】
</span><span>//</span><span>Data Annotations：</span>
[Table(<span>"</span><span>MyLodging</span><span>"</span><span>)]
</span><span>public</span> <span>class</span><span> Lodging
{
}

</span><span>//</span><span>Fluent API</span>
modelBuilder.Entity<lodging>().ToTable(<span>"</span><span>MyLodging</span><span>"</span><span>);

</span><span>//</span><span>【列名】
</span><span>//</span><span>Data Annotations：</span>
[Column(<span>"</span><span>MyName</span><span>"</span><span>)]
</span><span>public</span> <span>string</span> Name { <span>get</span>; <span>set</span><span>; }

</span><span>//</span><span>Fluent API:</span>
modelBuilder.Entity<lodging>().Property(p => p.Name).HasColumnName(<span>"</span><span>MyName</span><span>"</span><span>);

</span><span>//</span><span>【自增长】
</span><span>//</span><span>Data Annotations</span>
<span>[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]  Guid类型的主键、自增长
</span><span>public</span> Guid SocialId { <span>get</span>; <span>set</span><span>; }

</span><span>//</span><span>Fluent API:</span>
modelBuilder.Entity<person>().Property(p =><span> p.SocialId).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

</span><span>//</span><span>【忽略列映射】
</span><span>//</span><span>Data Annotations：</span>
<span>[NotMapped]
</span><span>public</span> <span>string</span><span> Name
{
    </span><span>get</span><span>
    {
        </span><span>return</span> FirstName + <span>"</span> <span>"</span> +<span> LastName;
    }
}

</span><span>//</span><span>Fluent API：</span>
modelBuilder.Entity<person>().Ignore(p =><span> p.Name);

</span><span>//</span><span>【忽略表映射】
</span><span>//</span><span>Data Annotations：</span>
<span>[NotMapped]
</span><span>public</span> <span>class</span><span> Person
{ }

</span><span>//</span><span>Fluent API:</span>
modelBuilder.Ignore<person><span>();

</span><span>//</span><span>【时间戳】
</span><span>//</span><span>Data Annotations：Timestamp</span>
<span>1441598336
</span><span>public</span> Byte[] TimeStamp { <span>get</span>; <span>set</span><span>; }   只能是byte类型

</span><span>//</span><span>Fluent API:</span>
modelBuilder.Entity<lodging>().Property(p =><span> p.TimeStamp).IsRowVersion();

</span><span>//</span><span>【复杂类型】
</span><span>//</span><span>Data Annotations：</span>
<span> [ComplexType]
 </span><span>public</span> <span>class</span><span> Address
 {
     </span><span>public</span> <span>string</span> Country { <span>get</span>; <span>set</span><span>; }
     </span><span>public</span> <span>string</span> City { <span>get</span>; <span>set</span><span>; }
 }

</span><span>//</span><span>Fluent API:</span>
modelBuilder.ComplexType<address>();</address></lodging></person></person></person></lodging></lodging></lodging></destination></destination></destination></lodging></destination>