Handle Entity Framework OptimisticConcurrencyException

Evaluating the .NET Entity Framework I try to find the right patterns to handle concurrent updates with optimistic concurrency mode.

In the documentation and many other places I see the following pattern:

Try
  ' Try to save changes, which may cause a conflict. 
  Dim num As Integer = context.SaveChanges()
  Console.WriteLine("No conflicts. " & num.ToString() & " updates saved.")
Catch generatedExceptionName As OptimisticConcurrencyException
  ' Resolve the concurrency conflict by refreshing the 
  ' object context before re-saving changes. 
  context.Refresh(RefreshMode.ClientWins, orders)

  ' Save changes. 
  context.SaveChanges()
  Console.WriteLine("OptimisticConcurrencyException handled and changes saved")
End Try

I see the following problems with this

• it automatically implements last-in-wins instead of using optimistic mode
• it is not robust: concurrent changes between .Refresh and .SaveChanges can cause a new OptimisticConcurrencyException

Is this correct, or am I missing something?

In a UI I normally let the user resolve the concurrency conflict:

Try
   _ctx.SaveChanges()
Catch ex As OptimisticConcurrencyException
   MessageBox.Show("Data was modified by another User." & vbCrLf &
   "Click 'Refresh' to show the current values and reapply your changes.",
   "Concurrency Violation", MessageBoxButton.OK)
End Try

In business logic I normally use a retry loop around the whole business transaction (reading and updating):

Const maxRetries = 5, retryDelayMs = 500
For i = 1 To maxRetries
    Try
        Using ctx As New EFConcurrencyTest.ConcurrencyTestEntities
            ctx.Inventories.First.QuantityInStock += 1
            System.Threading.Thread.Sleep(3000) 'Cause conflict
            ctx.SaveChanges()
        End Using
        Exit For
    Catch ex As OptimisticConcurrencyException
        If i = maxRetries Then Throw
        System.Threading.Thread.Sleep(retryDelayMs)
    End Try
Next

With EF I plan to encapsulate the loop:

ExecuteOptimisticSubmitChanges(Of EFConcurrencyTest.ConcurrencyTestEntities)(
    Sub(ctx)
        ctx.Inventories.First.QuantityInStock += 1
        System.Threading.Thread.Sleep(3000) 'Cause conflict
    End Sub)

See:

Functional Optimistic Concurrency in C#

Retryable actions in C#