實作自訂資料類別介面 (Entity Framework)

搭配 Entity Data Model (EDM) 使用自訂資料類別的建議方式是從 EntityObject 和 ComplexObject 繼承。如果您無法從 EntityObject 和 ComplexObject 繼承，或是您需要獨立於架構之外的更高獨立性，Entity Framework 提供了一組自訂資料類別介面。如果您不是繼承自 EntityObject，您必須實作這些介面來搭配 EDM 使用自訂資料類別。您實作的特定介面取決於自訂資料類別和應用程式的需求而定。

• IEntityWithChangeTracker
  變更追蹤所需。可讓物件服務追蹤物件的變更。

  物件服務會針對 IEntityChangeTracker 介面提供物件，好讓物件報告變更。IEntityWithChangeTracker 會定義 SetChangeTracker 方法。此方法會指定用來報告變更的 IEntityChangeTracker。如需詳細資訊，請參閱報告自訂資料類別中的變更 (Entity Framework)。

• IEntityWithKey
  選擇項。公開實體索引鍵給物件服務，以改善效能。

  IEntityWithKey 會定義 EntityKey 屬性。物件服務會使用 EntityKey 屬性，在物件內容中管理物件。

  如果您選擇不實作 IEntityWithKey，則載入相關物件、將物件附加至物件內容，或進行需要索引鍵的任何作業時，您將會發現效能降低和記憶體用量增加。

• IEntityWithRelationships
  具有關聯的實體都必須具備。可讓物件服務管理物件之間的關聯性。

  IEntityWithRelationships 會定義 RelationshipManager 屬性。物件服務會使用 RelationshipManager 屬性來存取用來管理與其他物件之關聯性的 RelationshipManager。

如需詳細資訊，請參閱 HOW TO：實作自訂資料類別介面 (Entity Framework)。

就像繼承自 EntityObject 的自訂資料類別一樣，實作這些介面的類別必須符合以下需求：

• 概念結構定義語言 (CSDL) 檔中定義的每一個實體類型都必須有一個物件。

• 命名空間、類別和資料屬性都必須套用適當的 EDM 屬性。

• 已套用 EDM 屬性 (Attribute) 的命名空間、類別和資料屬性 (Property) 名稱都必須符合對應 CSDL 檔案中的名稱。

如需詳細資訊，請參閱自訂物件 (Entity Framework)。

下列範例顯示針對 Order 物件實作這些介面所需的程式碼，其中 Order 是根據 SalesOrderHeader 資料表。

Dim _changeTracker As IEntityChangeTracker = Nothing

' Specify the IEntityChangeTracker to use for tracking changes.
Private Sub SetChangeTracker(ByVal changeTracker As IEntityChangeTracker) _
    Implements IEntityWithChangeTracker.SetChangeTracker
    _changeTracker = changeTracker

    ' Every time the change tracker is set, we must also set all the 
    ' complex type change trackers.
    If Not _extendedInfo Is Nothing Then
        _extendedInfo.SetComplexChangeTracker("ExtendedInfo", _changeTracker)
    End If
End Sub

Dim _entityKey As EntityKey = Nothing

' Define the EntityKey property for the class.
Property EntityKey() As EntityKey Implements IEntityWithKey.EntityKey
    Get
        Return _entityKey
    End Get
    Set(ByVal value As EntityKey)
        ' Set the EntityKey property, if it is not set.
        ' Report the change if the change tracker exists.
        If Not _changeTracker Is Nothing Then
            _changeTracker.EntityMemberChanging(StructuralObject.EntityKeyPropertyName)
            _entityKey = value
            _changeTracker.EntityMemberChanged(StructuralObject.EntityKeyPropertyName)
        Else
            _entityKey = value
        End If
    End Set
End Property

Dim _relationships As RelationshipManager = Nothing

' Define a relationship manager for the class.
ReadOnly Property RelationshipManager() As RelationshipManager _
Implements IEntityWithRelationships.RelationshipManager
    Get
        If _relationships Is Nothing Then
            _relationships = RelationshipManager.Create(Me)
        End If
        Return _relationships
    End Get
End Property

IEntityChangeTracker _changeTracker = null;

// Specify the IEntityChangeTracker to use for tracking changes.
void IEntityWithChangeTracker.SetChangeTracker(IEntityChangeTracker changeTracker)
{
    _changeTracker = changeTracker;

    // Every time the change tracker is set, we must also set all the 
    // complex type change trackers.
    if (_extendedInfo != null)
    {
        _extendedInfo.SetComplexChangeTracker("ExtendedInfo", _changeTracker);
    }
}

EntityKey _entityKey = null;

// Define the EntityKey property for the class.
EntityKey IEntityWithKey.EntityKey
{
    get 
    { 
        return _entityKey; 
    }
    set
    {
        // Set the EntityKey property, if it is not set.
        // Report the change if the change tracker exists.
        if (_changeTracker != null)
        {
            _changeTracker.EntityMemberChanging(StructuralObject.EntityKeyPropertyName);
            _entityKey = value;
            _changeTracker.EntityMemberChanged(StructuralObject.EntityKeyPropertyName);
        }
        else
        {
            _entityKey = value;
        }
    }
}

RelationshipManager _relationships = null;

// Define a relationship manager for the class.
RelationshipManager IEntityWithRelationships.RelationshipManager
{
    get
    {
        if (null == _relationships)
            _relationships = RelationshipManager.Create(this);
        return _relationships;
    }
}

複雜類型

複雜類型是實體類型的非純量屬性，可在實體內組織純量屬性。如需詳細資訊，請參閱複雜類型 (EDM)。追蹤複雜類型物件中的變更時，您需要撰寫自訂變更追蹤程式碼。因此，建議您在可能的情況下最好能從 EntityObject 和 ComplexObject 繼承。無法針對複雜類型物件實作任何自訂資料類別介面。但是，您可以使用以下程序，使用非繼承自 ComplexObject 的複雜類型物件來實作變更追蹤。

附註
如果您選擇針對物件來實作自訂資料類別介面，但是也要繼承自 ComplexObject，您仍然必須實作自訂變更追蹤，如下列程序所述。

若要針對複雜類型物件實作變更追蹤

1. 針對實體類型實作自訂資料介面。如需詳細資訊，請參閱 HOW TO：實作自訂資料類別介面 (Entity Framework)。

2. 確定複雜類型已正確定義在 EDM 的概念和對應區段中。如需詳細資訊，請參閱複雜類型 (EDM)。

3. 定義稱為 ComplexTypeChangeTracker 的抽象基底類別。

   ' Base class for complex types that implements change tracking.
   Public MustInherit Class ComplexTypeChangeTracker
       Protected _complexChangeTracker As IEntityChangeTracker = Nothing
       Private _rootComplexPropertyName As String
   
       ' Gets an IEntityChangeTracker to call for properties change. 
       ' You must do this in order to track changes.
       Public Overridable Sub SetComplexChangeTracker( _
           ByVal rootComplexPropertyName As String, _
           ByVal complexChangeTracker As IEntityChangeTracker)
           _rootComplexPropertyName = rootComplexPropertyName
           _complexChangeTracker = complexChangeTracker
       End Sub
   
       ' Protected method that is called before the change for change tracking 
       ' each of the scalar properties in the complex type.
       Protected Sub ReportMemberChanging(ByVal scalarPropertyName As String)
           If Not _complexChangeTracker Is Nothing Then
               _complexChangeTracker.EntityComplexMemberChanging( _
                   _rootComplexPropertyName, Me, scalarPropertyName)
           End If
       End Sub
   
       ' Protected method that is called after the change for change tracking 
       ' each of the scalar properties in the complex type.
       Protected Sub ReportMemberChanged(ByVal scalarPropertyName As String)
           If Not _complexChangeTracker Is Nothing Then
               _complexChangeTracker.EntityComplexMemberChanged( _
                   _rootComplexPropertyName, Me, scalarPropertyName)
           End If
       End Sub
   End Class
   

   // Base class for complex types that implements change tracking.
   public abstract class ComplexTypeChangeTracker
   {
       protected IEntityChangeTracker _complexChangeTracker = null;
       private string _rootComplexPropertyName;
   
       // Gets an IEntityChangeTracker to call for properties change. 
       // You must do this in order to track changes.
       virtual public void SetComplexChangeTracker(string rootComplexPropertyName, IEntityChangeTracker complexChangeTracker)
       {
           _rootComplexPropertyName = rootComplexPropertyName;
           _complexChangeTracker = complexChangeTracker;
       }
   
       // Protected method that is called before the change for change tracking 
       // each of the scalar properties in the complex type.
       protected void ReportMemberChanging(string scalarPropertyName)
       {
           if (null != _complexChangeTracker)
           {
               _complexChangeTracker.EntityComplexMemberChanging(_rootComplexPropertyName,
                                                          this, scalarPropertyName);
           }
       }
   
       // Protected method that is called after the change for change tracking 
       // each of the scalar properties in the complex type.
       protected void ReportMemberChanged(string scalarPropertyName)
       {
           if (null != _complexChangeTracker)
           {
               _complexChangeTracker.EntityComplexMemberChanged(_rootComplexPropertyName,
                                                         this, scalarPropertyName);
           }
       }
   }
   

4. 定義繼承自 ComplexTypeChangeTracker 的複雜類型類別，並套用 EdmComplexTypeAttribute。

   <EdmComplexTypeAttribute(NamespaceName:="Microsoft.Samples.Edm", Name:="OrderInfo")> _
   Partial Public Class OrderInfo
       Inherits ComplexTypeChangeTracker
   

   [EdmComplexTypeAttribute(NamespaceName = "Microsoft.Samples.Edm", Name = "OrderInfo")]
   public partial class OrderInfo : ComplexTypeChangeTracker
   {
   

5. 在複雜類型類別中，覆寫 SetComplexChangeTracker 方法。

   Public Overrides Sub SetComplexChangeTracker(ByVal rootComplexPropertyName As String, _
       ByVal changeTracker As IEntityChangeTracker)
   
       ' Call SetChangeTracker on the base class to set the change tracker 
       ' and the name of the root complex type property on the entity.
       MyBase.SetComplexChangeTracker(rootComplexPropertyName, changeTracker)
   End Sub
   

   override public void SetComplexChangeTracker(string rootComplexPropertyName, IEntityChangeTracker changeTracker)
   {
       // Call SetChangeTracker on the base class to set the change tracker 
       // and the name of the root complex type property on the entity.
       base.SetComplexChangeTracker(rootComplexPropertyName, changeTracker);
   }
   

6. 在複雜類型的純量屬性上實作標準變更追蹤。如需詳細資訊，請參閱報告自訂資料類別中的變更 (Entity Framework)。

7. 將 EdmComplexPropertyAttribute 套用到實體類型中的複雜屬性，並加入 SetComplexChangeTracker 的呼叫，以便在複雜屬性變更時重設變更追蹤程式。

   <EdmComplexPropertyAttribute()> _
           Public Property ExtendedInfo() As OrderInfo
       Get
           Return _extendedInfo
       End Get
       Set(ByVal value As OrderInfo)
   
           ' For a complex type any changes in the complex type 
           ' properties all get tracked together.
           ' The change tracker may be Nothing during object materialization.
           If Not _changeTracker Is Nothing Then
   
               ' Since this is a complex property, we need to reset the change 
               ' tracker on the complex type. 
               If Not _extendedInfo Is Nothing Then
                   ' Reset the change tracker.
                   _extendedInfo.SetComplexChangeTracker("ExtendedInfo", Nothing)
               End If
   
               ' Report the change.
               _changeTracker.EntityMemberChanging("ExtendedInfo")
               _extendedInfo = value
               _changeTracker.EntityMemberChanging("ExtendedInfo")
   
           Else
               _extendedInfo = value
           End If
   
           ' Rest the change tracker. Complex type property cannot be Nothing.
           If Not _extendedInfo Is Nothing Then
               _extendedInfo.SetComplexChangeTracker("ExtendedInfo", _changeTracker)
           End If
       End Set
   End Property
   

   [EdmComplexPropertyAttribute()]
   public OrderInfo ExtendedInfo
   {
       get
       {
           return _extendedInfo;
       }
       set
       {
           // For a complex type any changes in the complex type 
           // properties all get tracked together.
           // The change tracker may be null during object materialization.
           if (_changeTracker != null)
           {
               // Since this is a complex property, we need to reset the change 
               // tracker on the complex type. 
               if (_extendedInfo != null)
               {
                   // Reset the change tracker.
                   _extendedInfo.SetComplexChangeTracker("ExtendedInfo", null);
               }
   
               // Report the change.
               _changeTracker.EntityMemberChanging("ExtendedInfo");
               _extendedInfo = value;
               _changeTracker.EntityMemberChanged("ExtendedInfo");
           }
           else
           {
               _extendedInfo = value;
           }
   
           // Reset the change tracker. Complex type property cannot be null.
           if (_extendedInfo != null)
           {
               _extendedInfo.SetComplexChangeTracker("ExtendedInfo", _changeTracker);
           }
       }
   }
   

8. 針對每一個複雜屬性重複步驟 4-7。

9. 在實體類型的 System.Data.Objects.DataClasses.IEntityWithChangeTracker.SetChangeTracker(System.Data.Objects.DataClasses.IEntityChangeTracker) 實作中，插入 SetComplexChangeTracker 的呼叫來設定變更追蹤程式。針對此類型中的每一個複雜屬性執行這個動作一次。

   ' Every time the change tracker is set, we must also set all the 
   ' complex type change trackers.
   If Not _extendedInfo Is Nothing Then
       _extendedInfo.SetComplexChangeTracker("ExtendedInfo", _changeTracker)
   End If
   

   // Every time the change tracker is set, we must also set all the 
   // complex type change trackers.
   if (_extendedInfo != null)
   {
       _extendedInfo.SetComplexChangeTracker("ExtendedInfo", _changeTracker);
   }
   

另請參閱

參考

EDM 產生器 (EdmGen.exe)

概念

物件服務概觀 (Entity Framework)