EF 4.1 How to merge a graph returned by web service into an existing context

I have a scenario where I need to merge in a large graph (over 2000 entities) returned by web service into existing DbContex开发者_运维问答t. So, my first try:

    ' get new object from web service
    Dim newCust = DAL.GetCustomer(ActiveCustomerView.CustomerID)

    ' attach the object graph into existing context
    context.Customers.Attach(newCust)

This create duplicate conflicts in case I try to attach objects containing entities that already exists in the context.

To avoid this problem I’m clearing the local data and then call AcceptAllChanges before attach:

        context.Orders.Local.Clear()
        context.OrderItems.Local.Clear()
        context.Messages.Local.Clear()
        context.Contacts.Local.Clear()
        context.Parcels.Local.Clear()
        context.CustomerTransactions.Local.Clear()
        context.ReturnedParcels.Local.Clear()
        context.ReturnedOrderItems.Local.Clear()
        context.InventoryItems.Local.Clear()
        context.Shippments.Local.Clear()
        context.Prints.Local.Clear()

        DirectCast(context, IObjectContextAdapter).ObjectContext().AcceptAllChanges()

This works but the performance is not acceptable as it takes over 40 sec to clear the data.

Is there any other way to effectively accomplish that? Can I dispose somehow DbSet's instate of clearing them?

I can’t destroy and create new context each time I need to attach the graph because it contains other objects that would get lost.