Entity Framework（一） 映射

　　ADO.NET Entity Framework通过Modeel First和DataBase First，提供了几个把数据库表映射到对象上的曾。通过Database First，可以从一个数据库架构开始，使用Visual Studio 项模版创建完整映射。还可以先用设计器（Model First）设计实体类，再把它映射到数据库上，在该数据库中，表和表之间的关系可以有完全不同的结构。

需要定义的层如下：

　　1、逻辑层--该层定义关系数据

　　2、概念层--该层定义.NET类

　　3、映射层--该层定义从.NET类到关系表和关系的映射。

(1)逻辑层--逻辑层由SSDL（存储架构定义语言定义，描述数据库表及其关系的结构。）

<edmx:StorageModels>
      <Schema Namespace="ExtjsmvcModel.Store" Alias="Self" Provider="System.Data.SqlClient" ProviderManifestToken="2008" xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator" xmlns="http://schemas.microsoft.com/ado/2009/02/edm/ssdl">
        <EntityContainer Name="ExtjsmvcModelStoreContainer">
          <EntitySet Name="beian" EntityType="ExtjsmvcModel.Store.beian" store:Type="Tables" Schema="dbo" />
          <EntitySet Name="Menu" EntityType="ExtjsmvcModel.Store.Menu" store:Type="Tables" Schema="dbo" />
          <EntitySet Name="Users" EntityType="ExtjsmvcModel.Store.Users" store:Type="Tables" Schema="dbo" />
        </EntityContainer>
        <EntityType Name="beian">
          <Key>
            <PropertyRef Name="ID" />
          </Key>
          <Property Name="ID" Type="int" Nullable="false" StoreGeneratedPattern="Identity" />
          <Property Name="kehu_name" Type="varchar" MaxLength="50" />
          <Property Name="beianhao" Type="varchar" MaxLength="100" />
          <Property Name="beianpass" Type="varchar" MaxLength="100" />
          <Property Name="beianemail" Type="varchar" MaxLength="100" />
          <Property Name="emailpass" Type="varchar" MaxLength="100" />
          <Property Name="beianzh" Type="varchar" MaxLength="100" />
          <Property Name="beianzhpa" Type="varchar" MaxLength="100" />
        </EntityType>
        <EntityType Name="Menu">
          <Key>
            <PropertyRef Name="ID" />
          </Key>
          <Property Name="ID" Type="int" Nullable="false" StoreGeneratedPattern="Identity" />
          <Property Name="Menuname" Type="varchar" MaxLength="100" />
          <Property Name="ParentID" Type="int" />
          <Property Name="cls" Type="varchar" MaxLength="100" />
        </EntityType>
        <EntityType Name="Users">
          <Key>
            <PropertyRef Name="UserId" />
          </Key>
          <Property Name="UserId" Type="int" Nullable="false" />
          <Property Name="UserName" Type="varchar" MaxLength="100" />
          <Property Name="UserPwd" Type="varchar" MaxLength="100" />
        </EntityType>
      </Schema>
    </edmx:StorageModels>

（2）概念层（定义.NET类）该层用CSDL--概念架构定义语言定义。

<edmx:ConceptualModels>
      <Schema Namespace="ExtjsmvcModel" Alias="Self" xmlns:annotation="http://schemas.microsoft.com/ado/2009/02/edm/annotation" xmlns="http://schemas.microsoft.com/ado/2008/09/edm">
        <EntityContainer Name="ExtjsmvcEntities" annotation:LazyLoadingEnabled="true">
          <EntitySet Name="beian" EntityType="ExtjsmvcModel.beian" />
          <EntitySet Name="Menu" EntityType="ExtjsmvcModel.Menu" />
          <EntitySet Name="Users" EntityType="ExtjsmvcModel.Users" />
        </EntityContainer>
        <EntityType Name="beian">
          <Key>
            <PropertyRef Name="ID" />
          </Key>
          <Property Name="ID" Type="Int32" Nullable="false" annotation:StoreGeneratedPattern="Identity" />
          <Property Name="kehu_name" Type="String" MaxLength="50" Unicode="false" FixedLength="false" />
          <Property Name="beianhao" Type="String" MaxLength="100" Unicode="false" FixedLength="false" />
          <Property Name="beianpass" Type="String" MaxLength="100" Unicode="false" FixedLength="false" />
          <Property Name="beianemail" Type="String" MaxLength="100" Unicode="false" FixedLength="false" />
          <Property Name="emailpass" Type="String" MaxLength="100" Unicode="false" FixedLength="false" />
          <Property Name="beianzh" Type="String" MaxLength="100" Unicode="false" FixedLength="false" />
          <Property Name="beianzhpa" Type="String" MaxLength="100" Unicode="false" FixedLength="false" />
        </EntityType>
        <EntityType Name="Menu">
          <Key>
            <PropertyRef Name="ID" />
          </Key>
          <Property Name="ID" Type="Int32" Nullable="false" annotation:StoreGeneratedPattern="Identity" />
          <Property Name="Menuname" Type="String" MaxLength="100" Unicode="false" FixedLength="false" />
          <Property Name="ParentID" Type="Int32" />
          <Property Name="cls" Type="String" MaxLength="100" Unicode="false" FixedLength="false" />
        </EntityType>
        <EntityType Name="Users">
          <Key>
            <PropertyRef Name="UserId" />
          </Key>
          <Property Name="UserId" Type="Int32" Nullable="false" />
          <Property Name="UserName" Type="String" MaxLength="100" Unicode="false" FixedLength="false" />
          <Property Name="UserPwd" Type="String" MaxLength="100" Unicode="false" FixedLength="false" />
        </EntityType>
      </Schema>
    </edmx:ConceptualModels>

（3）映射层（映射层使用MSL--映射规范语言 把CSDL中的实体类型定义映射到SSDL中）

<edmx:Mappings>
      <Mapping Space="C-S" xmlns="http://schemas.microsoft.com/ado/2008/09/mapping/cs">
        <EntityContainerMapping StorageEntityContainer="ExtjsmvcModelStoreContainer" CdmEntityContainer="ExtjsmvcEntities">
          <EntitySetMapping Name="beian">
            <EntityTypeMapping TypeName="ExtjsmvcModel.beian">
              <MappingFragment StoreEntitySet="beian">
                <ScalarProperty Name="ID" ColumnName="ID" />
                <ScalarProperty Name="kehu_name" ColumnName="kehu_name" />
                <ScalarProperty Name="beianhao" ColumnName="beianhao" />
                <ScalarProperty Name="beianpass" ColumnName="beianpass" />
                <ScalarProperty Name="beianemail" ColumnName="beianemail" />
                <ScalarProperty Name="emailpass" ColumnName="emailpass" />
                <ScalarProperty Name="beianzh" ColumnName="beianzh" />
                <ScalarProperty Name="beianzhpa" ColumnName="beianzhpa" />
              </MappingFragment>
            </EntityTypeMapping>
          </EntitySetMapping>
          <EntitySetMapping Name="Menu">
            <EntityTypeMapping TypeName="ExtjsmvcModel.Menu">
              <MappingFragment StoreEntitySet="Menu">
                <ScalarProperty Name="ID" ColumnName="ID" />
                <ScalarProperty Name="Menuname" ColumnName="Menuname" />
                <ScalarProperty Name="ParentID" ColumnName="ParentID" />
                <ScalarProperty Name="cls" ColumnName="cls" />
              </MappingFragment>
            </EntityTypeMapping>
          </EntitySetMapping>
          <EntitySetMapping Name="Users">
            <EntityTypeMapping TypeName="ExtjsmvcModel.Users">
              <MappingFragment StoreEntitySet="Users">
                <ScalarProperty Name="UserId" ColumnName="UserId" />
                <ScalarProperty Name="UserName" ColumnName="UserName" />
                <ScalarProperty Name="UserPwd" ColumnName="UserPwd" />
              </MappingFragment>
            </EntityTypeMapping>
          </EntitySetMapping>
        </EntityContainerMapping>
      </Mapping>
    </edmx:Mappings>

　　用设计器和CSDL创建的实体类一般派生自基类EntityObject。

　　例如Users类派生自基类EntityObject，并为其数据定义属性，如UserName。这些属性的set访问器以两种不同的方式触发信息的改变：

　　一种方式是调用EntityObject基类的ReportPropertyChanging()和ReportPropertyChanged()方法。调用这些方法会使用INotifyProperty Changing和INotifyPropertyChanged接口，以通知每个客户端用这些接口的事件来注册。

　　另一种方式使用用部分方法，如OnTitleChanging()和OnTitleChanged()。他们默认没有实现方式，但可以在这个类的自定义扩展中实现他们。