ObjectContext.SavingChanges Evento

Definición

Espacio de nombres:

System.Data.Objects

Ensamblado:

System.Data.Entity.dll

Se produce cuando se guardan cambios en el origen de datos.

public:
 event EventHandler ^ SavingChanges;

public event EventHandler SavingChanges;

member this.SavingChanges : EventHandler 

Public Custom Event SavingChanges As EventHandler 

Tipo de evento

EventHandler

Ejemplos

En este ejemplo se registra un controlador para el SavingChanges evento que realiza la validación del estado de entidad.

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"));
                    }
                }
            }
        }
    }
}

Comentarios

El evento SavingChanges se genera al principio de una operación SaveChanges en un ObjectContext. Este evento normalmente se usa para validar los objetos modificados antes de que los nuevos valores se escriban en la base de datos.

Consulte también

• Trabajar con objetos (Entity Framework)