.net 实体框架:模型优先,继承?
我有一个Person表、一个Employee表和一个Contractor表。所有员工都是人,所有承包商都是人,每个人都是员工或承包商。像这样:.net 实体框架:模型优先,继承?,.net,entity-framework,inheritance,ef-model-first,.net,Entity Framework,Inheritance,Ef Model First,我有一个Person表、一个Employee表和一个Contractor表。所有员工都是人,所有承包商都是人,每个人都是员工或承包商。像这样: 我怎样才能首先使用模型来实现这个概念?继承?您有三种选择: 1-每个层次结构的表格: 性能良好,因为需要一个物理表。您需要向个人添加一个鉴别器字段,例如“PersonType”。这种方法的问题(我发现)是,最终会出现大量可为空的字段,并且派生类型之间的导航属性很难(以我的经验) 2-每种类型的表格: 需要单独的表,但如果您想创建另一个“Person”类型
我怎样才能首先使用模型来实现这个概念?继承?您有三种选择: 1-每个层次结构的表格: 性能良好,因为需要一个物理表。您需要向个人添加一个鉴别器字段,例如“PersonType”。这种方法的问题(我发现)是,最终会出现大量可为空的字段,并且派生类型之间的导航属性很难(以我的经验) 2-每种类型的表格: 需要单独的表,但如果您想创建另一个“Person”类型,则这有利于灵活性 3-每种混凝土类型的表:没有这方面的经验,因此无法对其进行评论。好吧,这和TPT非常相似 我可能会选择TPT,只是因为它更容易 尽管如此,“Contractor”和“Employee”表中的字段是同一类型的,因此您可以将其概括为具有TPH的单个字段。但我猜这不是完整的模型 模型优先的步骤:
表结构+继承==TPT。在designer中,它将如下所示: …和实体的原始EDMX以及到这些表的映射:
<?xml version="1.0" encoding="utf-8"?>
<edmx:Edmx Version="2.0" xmlns:edmx="http://schemas.microsoft.com/ado/2008/10/edmx" xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator" xmlns:ssdl="http://schemas.microsoft.com/ado/2009/02/edm/ssdl" xmlns:edm="http://schemas.microsoft.com/ado/2008/09/edm" xmlns:annotation="http://schemas.microsoft.com/ado/2009/02/edm/annotation" xmlns:map="http://schemas.microsoft.com/ado/2008/09/mapping/cs" xmlns:codegen="http://schemas.microsoft.com/ado/2006/04/codegeneration" xmlns:huagati="http://www.huagati.com/edmxtools/annotations">
<!--Updated by Huagati EDMX Tools version 2.16.4007.30259 on 2010-12-23 09:13:27-->
<!-- EF Runtime content -->
<edmx:Runtime>
<!-- SSDL content -->
<edmx:StorageModels>
<Schema xmlns="http://schemas.microsoft.com/ado/2009/02/edm/ssdl" Namespace="Model1.Store" Alias="Self" Provider="System.Data.SqlClient" ProviderManifestToken="2008">
<EntityContainer Name="Model1TargetContainer">
<EntitySet Name="Person" store:Type="Tables" Schema="dbo" Table="Person" store:Name="Person" EntityType="Model1.Store.Person" />
<EntitySet Name="Employee" store:Type="Tables" Schema="dbo" Table="Employee" store:Name="Employee" EntityType="Model1.Store.Employee" />
<AssociationSet Name="FK_Employee_Person" Association="Model1.Store.FK_Employee_Person">
<End Role="Person" EntitySet="Person" />
<End Role="Employee" EntitySet="Employee" />
</AssociationSet>
<EntitySet Name="Contractor" store:Type="Tables" Schema="dbo" Table="Contractor" store:Name="Contractor" EntityType="Model1.Store.Contractor" />
<AssociationSet Name="FK_Contractor_Person" Association="Model1.Store.FK_Contractor_Person">
<End Role="Person" EntitySet="Person" />
<End Role="Contractor" EntitySet="Contractor" />
</AssociationSet>
</EntityContainer>
<EntityType Name="Person">
<Documentation />
<Key>
<PropertyRef Name="PersonId" />
</Key>
<Property Name="PersonId" Type="bigint" Nullable="false" StoreGeneratedPattern="Identity" />
<Property Name="Name" Type="nvarchar" Nullable="true" MaxLength="50" />
</EntityType>
<EntityType Name="Employee">
<Documentation />
<Key>
<PropertyRef Name="EmployeeId" />
</Key>
<Property Name="EmployeeId" Type="bigint" Nullable="false" />
<Property Name="EmployeeNumber" Type="nvarchar" Nullable="true" MaxLength="50" />
</EntityType>
<Association Name="FK_Employee_Person">
<End Multiplicity="1" Role="Person" Type="Model1.Store.Person" />
<End Multiplicity="0..1" Role="Employee" Type="Model1.Store.Employee" />
<ReferentialConstraint>
<Principal Role="Person">
<PropertyRef Name="PersonId" />
</Principal>
<Dependent Role="Employee">
<PropertyRef Name="EmployeeId" />
</Dependent>
</ReferentialConstraint>
</Association>
<EntityType Name="Contractor">
<Documentation />
<Key>
<PropertyRef Name="ContractorId" />
</Key>
<Property Name="ContractorId" Type="bigint" Nullable="false" />
<Property Name="ContractorNumber" Type="nvarchar" Nullable="true" MaxLength="50" />
</EntityType>
<Association Name="FK_Contractor_Person">
<End Multiplicity="1" Role="Person" Type="Model1.Store.Person" />
<End Multiplicity="0..1" Role="Contractor" Type="Model1.Store.Contractor" />
<ReferentialConstraint>
<Principal Role="Person">
<PropertyRef Name="PersonId" />
</Principal>
<Dependent Role="Contractor">
<PropertyRef Name="ContractorId" />
</Dependent>
</ReferentialConstraint>
</Association>
</Schema>
</edmx:StorageModels>
<!-- CSDL content -->
<edmx:ConceptualModels>
<Schema xmlns="http://schemas.microsoft.com/ado/2008/09/edm" xmlns:cg="http://schemas.microsoft.com/ado/2006/04/codegeneration" xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator" Namespace="Model1" Alias="Self" xmlns:annotation="http://schemas.microsoft.com/ado/2009/02/edm/annotation">
<EntityContainer Name="Model1Container" annotation:LazyLoadingEnabled="true">
<EntitySet Name="Person" EntityType="Model1.Person" huagati:InheritanceStrategy="TPT" />
</EntityContainer>
<EntityType Name="Person">
<Key>
<PropertyRef Name="PersonId" />
</Key>
<Property Type="Int64" Name="PersonId" Nullable="false" annotation:StoreGeneratedPattern="Identity" />
<Property Type="String" Name="Name" Unicode="true" MaxLength="50" Nullable="true" />
</EntityType>
<EntityType Name="Employee" BaseType="Model1.Person">
<Property Type="String" Name="EmployeeNumber" Unicode="true" MaxLength="50" Nullable="true" />
</EntityType>
<EntityType Name="Contractor" BaseType="Model1.Person">
<Property Type="String" Name="ContractorNumber" Nullable="true" Unicode="true" MaxLength="50" />
</EntityType>
</Schema>
</edmx:ConceptualModels>
<!-- C-S mapping content -->
<edmx:Mappings>
<Mapping xmlns="http://schemas.microsoft.com/ado/2008/09/mapping/cs" Space="C-S">
<Alias Key="Model" Value="Model1" />
<Alias Key="Target" Value="Model1.Store" />
<EntityContainerMapping CdmEntityContainer="Model1Container" StorageEntityContainer="Model1TargetContainer">
<EntitySetMapping Name="Person">
<EntityTypeMapping TypeName="IsTypeOf(Model1.Person)">
<MappingFragment StoreEntitySet="Person">
<ScalarProperty Name="PersonId" ColumnName="PersonId" />
<ScalarProperty Name="Name" ColumnName="Name" />
</MappingFragment>
</EntityTypeMapping>
<EntityTypeMapping TypeName="IsTypeOf(Model1.Employee)">
<MappingFragment StoreEntitySet="Employee">
<ScalarProperty Name="PersonId" ColumnName="EmployeeId" />
<ScalarProperty Name="EmployeeNumber" ColumnName="EmployeeNumber" />
</MappingFragment>
</EntityTypeMapping>
<EntityTypeMapping TypeName="IsTypeOf(Model1.Contractor)">
<MappingFragment StoreEntitySet="Contractor">
<ScalarProperty Name="PersonId" ColumnName="ContractorId" />
<ScalarProperty Name="ContractorNumber" ColumnName="ContractorNumber" />
</MappingFragment>
</EntityTypeMapping>
</EntitySetMapping>
</EntityContainerMapping>
</Mapping>
</edmx:Mappings>
</edmx:Runtime>
<!-- EF Designer content (DO NOT EDIT MANUALLY BELOW HERE) -->
<edmx:Designer xmlns="http://schemas.microsoft.com/ado/2008/10/edmx">
<edmx:Connection>
<DesignerInfoPropertySet>
<DesignerProperty Name="MetadataArtifactProcessing" Value="EmbedInOutputAssembly" />
</DesignerInfoPropertySet>
</edmx:Connection>
<edmx:Options>
<DesignerInfoPropertySet>
<DesignerProperty Name="ValidateOnBuild" Value="true" />
<DesignerProperty Name="EnablePluralization" Value="True" />
</DesignerInfoPropertySet>
</edmx:Options>
<!-- Diagram content (shape and connector positions) -->
<edmx:Diagrams>
<Diagram Name="Model1">
<EntityTypeShape EntityType="Model1.Person" Width="1.5" PointX="5.125" PointY="2.125" Height="1.4033821614583331" />
<EntityTypeShape EntityType="Model1.Employee" Width="1.5" PointX="3.875" PointY="4" Height="1.2110807291666665" />
<InheritanceConnector EntityType="Model1.Employee">
<ConnectorPoint PointX="5.875" PointY="3.5283821614583331" />
<ConnectorPoint PointX="5.875" PointY="3.76" />
<ConnectorPoint PointX="4.625" PointY="3.76" />
<ConnectorPoint PointX="4.625" PointY="4" />
</InheritanceConnector>
<EntityTypeShape EntityType="Model1.Contractor" Width="2" PointX="5.875" PointY="4" Height="1.2110807291666665" />
<InheritanceConnector EntityType="Model1.Contractor" ManuallyRouted="false">
<ConnectorPoint PointX="5.875" PointY="3.5283821614583331" />
<ConnectorPoint PointX="5.875" PointY="3.76" />
<ConnectorPoint PointX="6.875" PointY="3.76" />
<ConnectorPoint PointX="6.875" PointY="4" />
</InheritanceConnector>
</Diagram>
</edmx:Diagrams>
</edmx:Designer>
</edmx:Edmx>
…和…
嘿,那张照片看起来很亲昵!:):P你知道的!我偷走了你的判决。。。再好不过了,一切都很好。我希望你能得到一些答案。祝你好运