即使MSL在资源中，在运行时如何在EF模型的概念信息和商店信息之间转换？

编程问答 2022-08-12

问题描述

在另一篇文章（How can I extract the database table and column name for a property on an EF4 entity?）中，我提供了一个答案（页面顶部），用于在运行时从概念中提取实体框架模型的商店信息（表/列）信息（实体/属性表达）。通常，人们不需要这种功能-但有时它很有用，例如当您想为在运行时创建的数据库的实体表中添加附加索引时。

我的解决方案的 缺点 （请参见下文）是它要求MSL映射信息位于单独的文件中（即，主机项目将元数据复制到输出路径）或它的XML已经可用。如果MSL元数据作为程序集资源嵌入怎么办？ （XElement方法无法解析“ res：//”路径名！）然后如何获取映射（或映射的XML）？

任何解决方案（无论它使用XML，元数据工作区还是其他任何方法）都必须与面向.NET 4.7之前的平台（即.NET 4.6.1）的项目一起使用，才能与一起使用任何 EF模型（无论创建的是Model-First，Database-First还是Code-First），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，它还应与DbContext派生的上下文一起工作（尽管可以从DbContext提取ObjectContext）并在VB.NET中。 （我目前正在将Visual Basic 2019与EF 6.4结合使用，而我的“宿主项目”则针对.NET 4.6.1。）

从角度来看，这是我的现有解决方案的代码（请记住我要缓解的上述限制）：

主机代码：（对于给定的XML示例（请参见底部），当给定实体“ Location”和实体时，它将返回表名“ Locations”和列名“ Address_Street”作为商店信息。属性表达式“ Address.Street” [和概念模型名称“ 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)

类代码： 

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，我从上面的代码中的“。\ SCTModel.msl”文件中加载了该文件：

<?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>

再次， 我的问题 从概念信息（实体/属性表达）中获取商店信息（表/列） ），将MSL映射信息作为资源嵌入到项目中（即“ res：//SCTModel.msl”）

解决方法

暂无找到可以解决该程序问题的有效方法，小编努力寻找整理中！

如果你已经找到好的解决方法，欢迎将解决方案带上本链接一起发送给小编。

小编邮箱:dio#foxmail.com (将#修改为@）

entity-frameworkentity-framework-6.4vb.netvb.net

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