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ObjectContext.SavingChanges Event

Occurs when changes are saved to the data source.

Namespace:  System.Data.Objects
Assembly:  System.Data.Entity (in System.Data.Entity.dll)

'Declaration
Public Event SavingChanges As EventHandler

The SavingChanges event is raised at the start of a SaveChanges operation on an ObjectContext. This event is typically used to validate changed objects before new values are written to the database.

This example is based on the Adventure Works Sales Model. This registers a handler for the SavingChanges event that performs entity state validation.


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


.NET Framework

Supported in: 4, 3.5 SP1

.NET Framework Client Profile

Supported in: 4

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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