在另一篇文章（如何为 EF4 实体上的属性提取数据库表和列名？）中，我提供了一个答案（页面顶部），用于在运行时提取实体框架模型的存储信息（表/列) 来自概念信息 ( entity/property-expression )。通常，不需要这样的功能——但有时它很有用，比如当你想为在运行时创建的数据库的实体表中添加额外的索引时。
我的解决方案（见下文）的缺点是它要求 MSL 映射信息位于单独的文件中（即宿主项目将元数据复制到输出路径）或其 XML 已经可用。如果 MSL 元数据作为程序集资源嵌入会怎样？（XElement 方法无法解析“res://”路径名！）那么如何获得映射（或映射的 XML）呢？
任何解决方案（无论是使用 XML、元数据工作区还是其他）都必须适用于针对 .NET 4.7 之前的平台（即 .NET 4.6.1）的项目，能够适用于任何EF 模型（无论无论是创建模型优先、数据库优先还是代码优先），并且能够处理复杂属性信息（即Entity.ComplexProperty. ... .ComplexSubProperty.ScalarProperty）以及标量属性信息。理想情况下，它还应该与 DbContext 派生的上下文一起使用（尽管可以从 DbContext 中提取 ObjectContext）并位于 VB.NET 中。（我目前正在使用带有 EF 6.4 的 Visual Basic 2019，并且我的“宿主项目”针对 .NET 4.6.1。）
从角度来看，这是我现有解决方案的代码（请记住我想要减轻的上述限制）：
主机代码：（对于给定的 XML 示例 [见底部]，当给定实体“Location”和属性表达式“Address.Street”[以及概念模型名称“SCTModel”]）：
Dim MSL As MSLMappingAction = New MSLMappingAction(".\SCTModel.msl", "SCTModel")
Dim ConceptualInfo As MSLConceptualInfo = New MSLConceptualInfo With {.EntityName = "Location", .PropertyName = "Address.Street"}
Dim StoreInfo As MSLStoreInfo = MSL.ConceptualToStore(ConceptualInfo)
MessageBox.Show(StoreInfo.TableName & ": " & StoreInfo.ColumnName)
班级代码：
Option Infer On
Imports System.Xml.Linq
''' <summary>
''' This class allows one to convert between an EF conceptual model's entity/property pair
''' and its database store's table/column pair.
''' </summary>
''' <remarks>It takes into account entity splitting and complex-property designations;
''' it DOES NOT take into account inherited properties
''' (in such a case, you should access the entity's base class)</remarks>
Public Class MSLMappingAction
' private fields and routines
Private mmaMSLMapping As XElement
Private mmaModelName, mmaNamespace As String
Private Function FullElementName(ByVal ElementName As String) As String
' pre-pend Namespace to ElementName
Return "{" & mmaNamespace & "}" & ElementName
End Function
Private Sub ValidateParams(ByVal MappingXML As XElement, Byval ModelName As String)
' verify that model name is specified
If String.IsNullOrEmpty(ModelName) Then
Throw New EntityException("Entity model name is not given!")
End If
' verify that we're using C-S space
If MappingXML.@Space <> "C-S" Then
Throw New MetadataException("XML is not C-S mapping data!")
End If
' get Namespace and set private variables
mmaNamespace = MappingXML.@xmlns
mmaMSLMapping = MappingXML : mmaModelName = ModelName
End Sub
Private Function IsSequenceEmpty(Items As IEnumerable(Of XElement)) As Boolean
' determine if query result is empty
Return _
Items Is Nothing OrElse Items.Count = 0
End Function
' properties
''' <summary>
''' Name of conceptual entity model
''' </summary>
''' <returns>Conceptual-model String</returns>
''' <remarks>Model name can only be set in constructor</remarks>
Public ReadOnly Property EntityModelName() As String
Get
Return mmaModelName
End Get
End Property
''' <summary>
''' Name of mapping namespace
''' </summary>
''' <returns>Namespace String of C-S mapping layer</returns>
''' <remarks>This value is determined when the XML mapping
''' is first parsed in the constructor</remarks>
Public ReadOnly Property MappingNamespace() As String
Get
Return mmaNamespace
End Get
End Property
' constructors
''' <summary>
''' Get C-S mapping information for an entity model (with XML tree)
''' </summary>
''' <param name="MappingXML">XML mapping tree</param>
''' <param name="ModelName">Conceptual-model name</param>
''' <remarks></remarks>
Public Sub New(ByVal MappingXML As XElement, ByVal ModelName As String)
ValidateParams(MappingXML, ModelName)
End Sub
''' <summary>
''' Get C-S mapping information for an entity model (with XML file)
''' </summary>
''' <param name="MSLFile">MSL mapping file</param>
''' <param name="ModelName">Conceptual-model name</param>
''' <remarks></remarks>
Public Sub New(ByVal MSLFile As String, ByVal ModelName As String)
Dim MappingXML As XElement = XElement.Load(MSLFile)
ValidateParams(MappingXML, ModelName)
End Sub
' methods
''' <summary>
''' Get C-S mapping infomration for an entity model (with XML String)
''' </summary>
''' <param name="XMLString">XML mapping String</param>
''' <param name="ModelName">Conceptual-model name</param>
''' <returns></returns>
Public Shared Function Parse(ByVal XMLString As String, ByVal ModelName As String)
Return New MSLMappingAction(XElement.Parse(XMLString), ModelName)
End Function
''' <summary>
''' Convert conceptual entity/property information into store table/column information
''' </summary>
''' <param name="ConceptualInfo">Conceptual-model data
''' (.EntityName = entity expression String, .PropertyName = property expression String)</param>
''' <returns>Store data (.TableName = table-name String, .ColumnName = column-name String)</returns>
''' <remarks></remarks>
Public Function ConceptualToStore(ByVal ConceptualInfo As MSLConceptualInfo) As MSLStoreInfo
Dim StoreInfo As New MSLStoreInfo
With ConceptualInfo
' prepare to query XML
If Not .EntityName.Contains(".") Then
' make sure entity name is fully qualified
.EntityName = mmaModelName & "." & .EntityName
End If
' separate property names if there's complex-type nesting
Dim Properties() As String = .PropertyName.Split(".")
' get relevant entity mapping
Dim MappingInfo As IEnumerable(Of XElement) = _
(From mi In mmaMSLMapping.Descendants(FullElementName("EntityTypeMapping")) _
Where mi.@TypeName = "IsTypeOf(" & .EntityName & ")" _
OrElse mi.@TypeName = .EntityName _
Select mi)
' make sure entity is in model
If IsSequenceEmpty(MappingInfo) Then
Throw New EntityException("Entity """ & .EntityName & """ was not found!")
End If
' get mapping fragments
Dim MappingFragments As IEnumerable(Of XElement) = _
(From mf In MappingInfo.Descendants(FullElementName("MappingFragment")) _
Select mf)
' make sure there's at least 1 fragment
If IsSequenceEmpty(MappingFragments) Then
Throw New EntityException("Entity """ & .EntityName & """ was not mapped!")
End If
' search each mapping fragment for the desired property
For Each MappingFragment In MappingFragments
' get physical table for this fragment
StoreInfo.TableName = MappingFragment.@StoreEntitySet
' search property expression chain
Dim PropertyMapping As IEnumerable(Of XElement) = {MappingFragment}
' parse complex property info (if any)
For index = 0 To UBound(Properties) - 1
' go down 1 level
Dim ComplexPropertyName = Properties(index)
PropertyMapping = _
(From pm In PropertyMapping.Elements(FullElementName("ComplexProperty")) _
Where pm.@Name = ComplexPropertyName)
' verify that the property specified for this level exists
If IsSequenceEmpty(PropertyMapping) Then
Exit For 'go to next fragment if not
End If
Next index
' property not found? try next fragment
If IsSequenceEmpty(PropertyMapping) Then
Continue For
End If
' parse scalar property info
Dim ScalarPropertyName = Properties(UBound(Properties))
Dim ColumnName As String = _
(From pm In PropertyMapping.Elements(FullElementName("ScalarProperty")) _
Where pm.@Name = ScalarPropertyName _
Select CN = pm.@ColumnName).FirstOrDefault
' verify that scalar property exists
If Not String.IsNullOrEmpty(ColumnName) Then
' yes? return (exit) with column info
StoreInfo.ColumnName = ColumnName : Return StoreInfo
End If
Next MappingFragment
' property wasn't found
Throw New EntityException("Property """ & .PropertyName _
& """ of entity """ & .EntityName & """ was not found!")
End With
End Function
End Class
''' <summary>
''' Conceptual-model entity and property information
''' </summary>
Public Structure MSLConceptualInfo
''' <summary>
''' Name of entity in conceptual model
''' </summary>
''' <value>Entity expression String</value>
''' <remarks>EntityName may or may not be fully qualified (i.e., "ModelName.EntityName");
''' when a mapping method is called by the MSLMappingAction class, the conceptual model's
''' name and a period will be pre-pended if it's omitted</remarks>
Public Property EntityName As String
''' <summary>
''' Name of property in entity
''' </summary>
''' <value>Property expression String</value>
''' <remarks>PropertyName may be either a stand-alone scalar property or a scalar property
''' within 1 or more levels of complex-type properties; in the latter case, it MUST be fully
''' qualified (i.e., "ComplexPropertyName.InnerComplexPropertyName.ScalarPropertyName")</remarks>
Public Property PropertyName As String
End Structure
''' <summary>
''' Database-store table and column information
''' </summary>
Public Structure MSLStoreInfo
''' <summary>
''' Name of table in database
''' </summary>
Public Property TableName As String
''' <summary>
''' Name of column in database table
''' </summary>
Public Property ColumnName As String
End Structure
这是示例XML——我从上面代码中的“.\SCTModel.msl”文件加载：
<?xml version="1.0" encoding="utf-8"?>
<Mapping Space="C-S" xmlns="http://schemas.microsoft.com/ado/2008/09/mapping/cs">
<EntityContainerMapping StorageEntityContainer="SCTModelStoreContainer" CdmEntityContainer="SocialContactsTracker">
<EntitySetMapping Name="SocialContacts">
<EntityTypeMapping TypeName="IsTypeOf(SCTModel.SocialContact)">
<MappingFragment StoreEntitySet="SocialContacts">
<ScalarProperty Name="Id" ColumnName="Id" />
<ScalarProperty Name="DateAdded" ColumnName="DateAdded" />
<ScalarProperty Name="Information" ColumnName="Information" />
<ComplexProperty Name="DefaultAssociations" TypeName="SCTModel.DefaultAssociations">
<ScalarProperty Name="DefaultLocationID" ColumnName="DefaultAssociations_DefaultLocationID" />
<ScalarProperty Name="DefaultEmailID" ColumnName="DefaultAssociations_DefaultEmailID" />
<ScalarProperty Name="DefaultPhoneNumberID" ColumnName="DefaultAssociations_DefaultPhoneNumberID" />
<ScalarProperty Name="DefaultWebsiteID" ColumnName="DefaultAssociations_DefaultWebsiteID" />
</ComplexProperty>
<ScalarProperty Name="Picture" ColumnName="Picture" />
</MappingFragment>
</EntityTypeMapping>
<EntityTypeMapping TypeName="IsTypeOf(SCTModel.Person)">
<MappingFragment StoreEntitySet="SocialContacts_Person">
<ScalarProperty Name="Id" ColumnName="Id" />
<ScalarProperty Name="DateOfBirth" ColumnName="DateOfBirth" />
<ScalarProperty Name="FirstName" ColumnName="FirstName" />
<ScalarProperty Name="LastName" ColumnName="LastName" />
</MappingFragment>
</EntityTypeMapping>
<EntityTypeMapping TypeName="IsTypeOf(SCTModel.Organization)">
<MappingFragment StoreEntitySet="SocialContacts_Organization">
<ScalarProperty Name="Id" ColumnName="Id" />
<ScalarProperty Name="Name" ColumnName="Name" />
<ScalarProperty Name="DateOfCreation" ColumnName="DateOfCreation" />
</MappingFragment>
</EntityTypeMapping>
</EntitySetMapping>
<EntitySetMapping Name="Locations">
<EntityTypeMapping TypeName="IsTypeOf(SCTModel.Location)">
<MappingFragment StoreEntitySet="Locations">
<ScalarProperty Name="Id" ColumnName="Id" />
<ScalarProperty Name="City" ColumnName="City" />
<ScalarProperty Name="State" ColumnName="State" />
<ScalarProperty Name="ZIP" ColumnName="ZIP" />
<ScalarProperty Name="Country" ColumnName="Country" />
<ComplexProperty Name="Address" TypeName="SCTModel.Address">
<ScalarProperty Name="Street" ColumnName="Address_Street" />
<ScalarProperty Name="Apartment" ColumnName="Address_Apartment" />
<ScalarProperty Name="HouseNumber" ColumnName="Address_HouseNumber" />
</ComplexProperty>
</MappingFragment>
</EntityTypeMapping>
</EntitySetMapping>
<EntitySetMapping Name="PhoneNumbers">
<EntityTypeMapping TypeName="IsTypeOf(SCTModel.PhoneNumber)">
<MappingFragment StoreEntitySet="PhoneNumbers">
<ScalarProperty Name="Id" ColumnName="Id" />
<ScalarProperty Name="Number" ColumnName="Number" />
<ScalarProperty Name="PhoneType" ColumnName="PhoneType" />
</MappingFragment>
</EntityTypeMapping>
</EntitySetMapping>
<EntitySetMapping Name="Emails">
<EntityTypeMapping TypeName="IsTypeOf(SCTModel.Email)">
<MappingFragment StoreEntitySet="Emails">
<ScalarProperty Name="Id" ColumnName="Id" />
<ScalarProperty Name="DomainName" ColumnName="DomainName" />
<ScalarProperty Name="UserName" ColumnName="UserName" />
</MappingFragment>
</EntityTypeMapping>
</EntitySetMapping>
<EntitySetMapping Name="Websites">
<EntityTypeMapping TypeName="IsTypeOf(SCTModel.Website)">
<MappingFragment StoreEntitySet="Websites">
<ScalarProperty Name="Id" ColumnName="Id" />
<ScalarProperty Name="URL" ColumnName="URL" />
</MappingFragment>
</EntityTypeMapping>
</EntitySetMapping>
<AssociationSetMapping Name="SocialContactWebsite" TypeName="SCTModel.SocialContactWebsite" StoreEntitySet="SocialContactWebsite">
<EndProperty Name="SocialContact">
<ScalarProperty Name="Id" ColumnName="SocialContacts_Id" />
</EndProperty>
<EndProperty Name="Website">
<ScalarProperty Name="Id" ColumnName="Websites_Id" />
</EndProperty>
</AssociationSetMapping>
<AssociationSetMapping Name="SocialContactPhoneNumber" TypeName="SCTModel.SocialContactPhoneNumber" StoreEntitySet="SocialContactPhoneNumber">
<EndProperty Name="SocialContact">
<ScalarProperty Name="Id" ColumnName="SocialContacts_Id" />
</EndProperty>
<EndProperty Name="PhoneNumber">
<ScalarProperty Name="Id" ColumnName="PhoneNumbers_Id" />
</EndProperty>
</AssociationSetMapping>
<AssociationSetMapping Name="SocialContactEmail" TypeName="SCTModel.SocialContactEmail" StoreEntitySet="SocialContactEmail">
<EndProperty Name="SocialContact">
<ScalarProperty Name="Id" ColumnName="SocialContacts_Id" />
</EndProperty>
<EndProperty Name="Email">
<ScalarProperty Name="Id" ColumnName="Emails_Id" />
</EndProperty>
</AssociationSetMapping>
<AssociationSetMapping Name="SocialContactLocation" TypeName="SCTModel.SocialContactLocation" StoreEntitySet="SocialContactLocation">
<EndProperty Name="SocialContact">
<ScalarProperty Name="Id" ColumnName="SocialContacts_Id" />
</EndProperty>
<EndProperty Name="Location">
<ScalarProperty Name="Id" ColumnName="Locations_Id" />
</EndProperty>
</AssociationSetMapping>
</EntityContainerMapping>
</Mapping>
再一次，当 MSL 映射信息作为资源嵌入到项目中时（即“res://SCTModel.msl”） ，我的问题是从概念信息（entity/property-expression ）获取商店信息（table/column ）