Replace B2BUA with a new one, without loosing transfer states

Question

I'm having some issues with replacing my B2BUA for transfer purpose.
I have a link between 2 participant by using a B2BUA. I want to transfer one of these participants into another B2BUA, and that new B2BUA will repaces the previous one. I can accomplish this succesfully without any troubles, by using self-transfer and B2BUA
utilitize.
But when the link is established in B2BUA between two participants, when creating a new B2BUA, the participants can still talk untill the new B2BUA is established (this is the issue).
I doesn't loose the link of participant in Call leg 1, since I'm using a Self-transfer leaving the call state as incoming. But if I call BeginTerminate() of the 1st B2BUA while establishing the 2nd B2BUA, then I'll loose my transfer states of the first Call,
and I'm using this event state to tell me when a transfer is succesfully done.
How can I cancel the stream between the two participants in the first B2BUA, as soon as I begin to establish the second B2BUA??

Answer 1

If either leg of the B2B is terminated, the B2B call is terminated. In a transfer scenario the leg of the participating in the self transfer will end before the transfer itself is completed, leading to an OperationFailureException on the EndTransfer. 
There is really no way to avoid this, so you should just expect it.
Here is a snip from one of my test programs:
private void InitiateSelfTransfer()
Console.WriteLine("Initiating self-transfer on p2p call...");
//Copy inCall since we will replace it with the new inCall prior to the completion of the transfer.
AudioVideoCall p2pOldInCall = (AudioVideoCall)inCall;
//Pass a reference to this instance in the Context so the new inbound call can reattach to this session.
p2pOldInCall.ApplicationContext = this;
p2pOldInCall.TransferStateChanged += new EventHandler<TransferStateChangedEventArgs>(oldInCall_TransferStateChanged);
CallTransferOptions cto = new CallTransferOptions(CallTransferType.Attended);
//Execute the transfer.
Console.WriteLine("Beginning Self-Transfer...");
try
p2pOldInCall.BeginTransfer(p2pOldInCall, cto,
ar =>
Console.WriteLine("Self-Transfer Completed...");
try
p2pOldInCall.EndTransfer(ar);
Console.WriteLine("Self-Transfer was successful!");
SendTransferNotification(200, "Succeeded at self-transfer");
//In this scenario the BackToBackCall seems to always terminate the call before we are made aware the transfer is complete.
//This operation has to execute as Attended, so we simply catch the exception generated, it doesn't seem to cause us any problems.
catch (OperationFailureException)
Console.WriteLine("Exception ignored on self-transfer...");
SendTransferNotification(487, "Call already terminated...");
catch (RealTimeException ex)
SendTransferNotification(503, "Failed on self-transfer of inbound leg");
Console.WriteLine(ex);
, null);
catch (InvalidOperationException iOpEx)
Console.WriteLine("Invalid Operation Exception: " + iOpEx.ToString());