如何提取EF4實體上的屬性的數據庫表和列名稱？

Question

我正在爲使用EF4作爲數據訪問層的應用程序編寫一個審計組件。我能夠非常容易地確定哪些實體已被修改，並且通過ObjectStateEntry對象可以提取已修改的原始值，當前值，實體名稱和屬性名稱，但我也想提取原始表並在SQL Server使用的列名（因爲他們並不總是符合模型的實體和屬性名）

有誰知道的一個很好的辦法做到這一點？它甚至有可能嗎？映射顯然存儲在MSL中，但我無法找到一種以編程方式訪問這些映射的方法。

Answer 1

我有點困惑，爲什麼在SQL Server中使用的原料表和列名不匹配模型的實體和屬性名。除用於提供多對多映射的表格之外，（通常）應該是對象名稱/屬性與表格名稱和列名稱之間的直接對應關係。

隨着中說，實體框架是一個ORM。框架的整個目的是爲數據庫提供一個面向對象的視圖，並將其抽象爲直接與關係數據庫進行交互。 EF並非真正意味着讓你繞開框架，而且據我所知，你期望做的事是不可能的。 （不過，如果我錯了，這是新的東西，我會今天獲悉，我會刪除或相應地編輯此答案。）

Answer 2

如果你寫的代碼審覈的映射，是不是你真正的審計/驗證微軟EF代碼？也許這可以安全地從問題領域界定出來，除非審計的目的是建立對EF本身的信心。

但如果你真的需要做這種審覈的，一種可能性是增加一個構建步驟嵌入.edmx文件在你檢查DLL的資源。你沒有說你是否對被測試的DLL有這樣的控制/輸入。然而，這將是一次黑客攻擊 - 正如JasCav所說，ORM的目的是爲了完成你想要的東西。

Answer 3

所有模型數據，可通過此方法 myObjectContext.MetadataWorkspace.GetEntityContainer(myObjectContext.DefaultContainerName, DataSpace.CSSpace);

認爲至少應該給你如何做你想做的一個開始。 DataSpace.CSSpace指定概念名稱和商店名稱之間的映射。 DataSpace.CSpace爲您提供了概念模型，DataSpace.SSpace爲您提供了存儲模型。

Answer 4

在看了一個實體框架模型設計器之後，我看到它使用EdmEntityTypeAttribute和DataMemberAttribute來修飾生成的類和屬性。它們中的每一個都有一個Name屬性，其中包含映射實體的名稱（分別爲表格和列）。當屬性名稱與列的名稱匹配時，設計者不會爲位置參數Name提供值。下面的代碼適用於我。

private static string GetTableName<T>() where T : EntityObject 
    { 
     Type type = typeof(T); 
     var at = GetAttribute<EdmEntityTypeAttribute>(type); 
     return at.Name; 
    } 

    private static string GetColumnName<T>(Expression<Func<T, object>> propertySelector) where T : EntityObject 
    { 
     Contract.Requires(propertySelector != null, "propertySelector is null."); 

     PropertyInfo propertyInfo = GetPropertyInfo(propertySelector.Body); 
     DataMemberAttribute attribute = GetAttribute<DataMemberAttribute>(propertyInfo); 
     if (String.IsNullOrEmpty(attribute.Name)) 
     { 
      return propertyInfo.Name; 
     } 
     return attribute.Name; 
    } 

    private static T GetAttribute<T>(MemberInfo memberInfo) where T : class 
    { 
     Contract.Requires(memberInfo != null, "memberInfo is null."); 
     Contract.Ensures(Contract.Result<T>() != null); 

     object[] customAttributes = memberInfo.GetCustomAttributes(typeof(T), false); 
     T attribute = customAttributes.Where(a => a is T).First() as T; 
     return attribute; 
    } 

    private static PropertyInfo GetPropertyInfo(Expression propertySelector) 
    { 
     Contract.Requires(propertySelector != null, "propertySelector is null."); 
     MemberExpression memberExpression = propertySelector as MemberExpression; 
     if (memberExpression == null) 
     { 
      UnaryExpression unaryExpression = propertySelector as UnaryExpression; 
      if (unaryExpression != null && unaryExpression.NodeType == ExpressionType.Convert) 
      { 
       memberExpression = unaryExpression.Operand as MemberExpression; 
      } 
     } 
     if (memberExpression != null && memberExpression.Member.MemberType == MemberTypes.Property) 
     { 
      return memberExpression.Member as PropertyInfo; 
     } 
     throw new ArgumentException("No property reference was found.", "propertySelector"); 
    } 

    // Invocation example 
    private static Test() 
    { 
     string table = GetTableName<User>(); 
     string column = GetColumnName<User>(u=>u.Name); 
    } 

Answer 5

這裏有一個概念和存儲的信息之間進行轉換的通用算法，用Visual Basic 2010

我寫了一個新的常規，爲實體/屬性對轉換成一個表/列對。這個類，MSLMappingAction，需要在其構造模型名稱以及一個的XElement XML樹，一個MSL映射文件，或XML字符串。然後使用ConceptualToStore方法取String指定實體和屬性「表達式」（存儲在MSLConceptualInfo結構中）並查找表名和列名（存儲在MSLStoreInfo結構中）。

注：

1. 你也可以寫一個「StoreToConceptual」方法在 轉換其他方向，但XML查詢可能會有點 更加複雜。這同樣適用於處理 導航屬性格式/功能/存儲過程映射。
2. 當心繼承派生實體的屬性！如果屬性 不特定的衍生實體，那麼你應該使用基本 實體的名稱。）

下面的代碼。

主機代碼：（對於給定的XML樣本[見底]，它給出的實體「位置」和屬性表達式時返回表名稱「位置」和列名「Address_Street」的店鋪信息「地址.Street」 [和概念模型名 「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) 

類代碼：

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 

美中不足的是，節點名稱都必須有一個命名空間預先給他們。它絆倒了我，直到我一次檢查了我的元素1！

這裏的樣品 XML - 這是我從加載「\ SCTModel.msl。」在上面的代碼文件：

<?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>