实现自定义数据类接口（实体框架）

若要将自定义数据类用于 Entity Data Model (EDM)，建议从 EntityObject 和 ComplexObject 继承。针对无法从 EntityObject 和 ComplexObject 继承，或者需要更加独立于框架的情况，Entity Framework 提供了一组自定义数据类接口。如果不从 EntityObject 继承，则必须实现这些接口，才能将自定义数据类用于 EDM。要实现的特定接口取决于自定义数据类和应用程序的要求。

• IEntityWithChangeTracker
  对于更改跟踪是必需的。使对象服务可以跟踪对对象的更改。

  对象服务向对象提供 IEntityChangeTracker 接口，使对象能够报告更改。IEntityWithChangeTracker 定义 SetChangeTracker 方法。此方法指定用于报告更改的 IEntityChangeTracker。有关更多信息，请参见报告自定义数据类中的更改（实体框架）。

• IEntityWithKey
  可选。向对象服务公开实体键以提高性能。

  IEntityWithKey 定义 EntityKey 属性。对象服务使用 EntityKey 属性来管理对象上下文中的对象。

  如果选择不实现 IEntityWithKey，则在加载相关对象、将对象附加到对象上下文或执行需要键的任何操作时，性能将会下降，内存占用量会增加。

• IEntityWithRelationships
  对于具有关联的实体，这是必需的。使对象服务能够管理对象之间的关系。

  IEntityWithRelationships 定义 RelationshipManager 属性。对象服务使用 RelationshipManager 属性来访问用于管理与其他对象的关系的 RelationshipManager。

有关更多信息，请参见如何：实现自定义数据类接口（实体框架）。

与从 EntityObject 继承的自定义数据类相似，实现这些接口的类必须满足以下要求：

• 在概念性架构定义语言 (CSDL) 文件中定义的每个实体类型都必须有一个对象。

• 命名空间、类和数据属性 (Property) 必须应用适当的 EDM 属性 (Attribute)。

• 应用了 EDM 属性 (Attribute) 的命名空间、类和数据属性 (Property) 的名称必须与相应的 CSDL 文件中的名称相匹配。

有关更多信息，请参见自定义对象（实体框架）。

下面的示例演示为 Order 对象实现这些接口所需的代码，其中 Order 基于 SalesOrderHeader 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;
    }
}

复杂类型

复杂类型是实体类型的非标量属性，实体类型允许在实体内组织标量属性。有关更多信息，请参见复杂类型 (EDM)。若要跟踪复杂类型对象中的更改，需要编写自定义更改跟踪代码。为此，建议尽可能从 EntityObject 和 ComplexObject 继承。没有自定义数据类接口可以实现复杂类型对象。不过，使用下面的过程可以实现不从 ComplexObject 继承的复杂类型对象的更改跟踪。

注意
如果选择为对象实现自定义数据类接口，同时还从 ComplexObject 继承，则必须还要实现自定义更改跟踪，如下面的过程所述。

实现复杂类型对象的更改跟踪

1. 实现实体类型的自定义数据接口。有关更多信息，请参见如何：实现自定义数据类接口（实体框架）。

2. 确保在 EDM 的概念性部分和映射部分中正确定义了复杂类型。有关更多信息，请参见复杂类型 (EDM)。

3. 定义名为 ComplexTypeChangeTracker 的抽象基类。

   ' 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. 定义从 ComplexTypeChangeTracker 继承的复杂类型类，并应用 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. 在复杂类型类中，重写 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. 对复杂类型的标量属性实现标准更改跟踪。有关更多信息，请参见报告自定义数据类中的更改（实体框架）。

7. 对实体类型的复杂属性应用 EdmComplexPropertyAttribute，并添加对 SetComplexChangeTracker 的调用，以便在复杂属性更改时重置更改跟踪器。

   <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. 对每个复杂属性重复步骤 4-7。

9. 在实体类型的 System.Data.Objects.DataClasses.IEntityWithChangeTracker.SetChangeTracker(System.Data.Objects.DataClasses.IEntityChangeTracker) 实现中，插入对 SetComplexChangeTracker 的调用以设置更改跟踪器。对类型中的每个复杂属性执行一次此步骤。

   ' 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);
   }
   

另请参见

参考

EDM 生成器 (EdmGen.exe)

概念

对象服务概述（实体框架）