實作自訂資料類別介面 (Entity Framework)

發行項
08/21/2008

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

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)。
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)。

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);
        }
    }
}

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
{

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);
}

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)。

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);
        }
    }
}

針對每一個複雜屬性重複步驟 4-7。

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);
}

共用方式為

實作自訂資料類別介面 (Entity Framework)

複雜類型

若要針對複雜類型物件實作變更追蹤

另請參閱

參考

概念

其他資源