ObjectContext.SavingChanges ObjectContext.SavingChanges ObjectContext.SavingChanges ObjectContext.SavingChanges Event

定義

當變更儲存至資料來源時發生。Occurs when changes are saved to the data source.

public:
 event EventHandler ^ SavingChanges;
public event EventHandler SavingChanges;
member this.SavingChanges : EventHandler 
Public Custom Event SavingChanges As EventHandler 

範例

這個範例根據AdventureWorks Sales ModelThis example is based on the AdventureWorks Sales Model. 這會針對執行實體狀態驗證的 SavingChanges 事件註冊處理常式。This registers a handler for the SavingChanges event that performs entity state validation.

public class AdventureWorksProxy
{
    // Define the object context to be provided.
    private AdventureWorksEntities contextProxy =
        new AdventureWorksEntities();

    public AdventureWorksProxy()
    {
        // When the object is initialized, register the 
        // handler for the SavingChanges event.
        contextProxy.SavingChanges
            += new EventHandler(context_SavingChanges);
    }

    // Method that provides an object context.
    public AdventureWorksEntities Context
    {
        get
        {
            return contextProxy;
        }
    }

    // SavingChanges event handler.
    private void context_SavingChanges(object sender, EventArgs e)
    {
        // Ensure that we are passed an ObjectContext
        ObjectContext context = sender as ObjectContext;
        if (context != null)
        {

            // Validate the state of each entity in the context
            // before SaveChanges can succeed.
            foreach (ObjectStateEntry entry in
                context.ObjectStateManager.GetObjectStateEntries(
                EntityState.Added | EntityState.Modified))
            {
                // Find an object state entry for a SalesOrderHeader object. 
                if (!entry.IsRelationship && (entry.Entity.GetType() == typeof(SalesOrderHeader)))
                {
                    SalesOrderHeader orderToCheck = entry.Entity as SalesOrderHeader;

                    // Call a helper method that performs string checking 
                    // on the Comment property.
                    string textNotAllowed = Validator.CheckStringForLanguage(
                        orderToCheck.Comment);

                    // If the validation method returns a problem string, raise an error.
                    if (!string.IsNullOrEmpty(textNotAllowed))
                    {
                        throw new ArgumentException(String.Format("Changes cannot be "
                            + "saved because the {0} '{1}' object contains a "
                            + "string that is not allowed in the property '{2}'.",
                            entry.State, "SalesOrderHeader", "Comment"));
                    }
                }
            }
        }
    }
}
Public Class AdventureWorksProxy
    ' Define the object context to be provided. 
    Private contextProxy As New AdventureWorksEntities()

    Public Sub New()
        ' When the object is initialized, register the 
        ' handler for the SavingChanges event. 
        AddHandler contextProxy.SavingChanges, AddressOf context_SavingChanges
    End Sub

    ' Method that provides an object context. 
    Public ReadOnly Property Context() As AdventureWorksEntities
        Get
            Return contextProxy
        End Get
    End Property

    ' SavingChanges event handler. 
    Private Sub context_SavingChanges(ByVal sender As Object, ByVal e As EventArgs)
        ' Ensure that we are passed an ObjectContext 
        Dim context As ObjectContext = TryCast(sender, ObjectContext)
        If context IsNot Nothing Then

            ' Validate the state of each entity in the context 
            ' before SaveChanges can succeed. 
            For Each entry As ObjectStateEntry In context.ObjectStateManager.GetObjectStateEntries(EntityState.Added Or EntityState.Modified)
                ' Find an object state entry for a SalesOrderHeader object. 
                If Not entry.IsRelationship AndAlso (entry.Entity.GetType() Is GetType(SalesOrderHeader)) Then
                    Dim orderToCheck As SalesOrderHeader = TryCast(entry.Entity, SalesOrderHeader)

                    ' Call a helper method that performs string checking 
                    ' on the Comment property. 
                    Dim textNotAllowed As String = Validator.CheckStringForLanguage(orderToCheck.Comment)

                    ' If the validation method returns a problem string, raise an error. 
                    If textNotAllowed <> String.Empty Then
                        Throw New ArgumentException(String.Format("Changes cannot be " & _
                                                                    "saved because the {0} '{1}' object contains a " & _
                                                                    "string that is not allowed in the property '{2}'.", _
                                                                    entry.State, "SalesOrderHeader", "Comment"))
                    End If
                End If
            Next
        End If
    End Sub
End Class

備註

SavingChanges 事件會針對 SaveChangesObjectContext 作業的開頭引發。The SavingChanges event is raised at the start of a SaveChanges operation on an ObjectContext. 這個事件通常是在新值寫入資料庫之前,用來驗證變更的物件。This event is typically used to validate changed objects before new values are written to the database.

適用於

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