declare       @Handle                    uniqueidentifier
             ,      @LockResult         int
 
       begin transaction
 
             select @Handle      = CEP.conversation_handle
             from   sys.conversation_endpoints CEP
             where  CEP.far_service = 'EventService'
                           and CEP.state = 'CO'
                           and CEP.is_initiator = 1
 
             if     @Handle is null 
             begin
                    exec @LockResult = sp_getapplock
                                  @Resource           = 'EventAsync_Lock'
                           ,      @LockMode           = 'Exclusive'
 
                    if     @LockResult < 0
                           ;throw...
 
                    -- вдруг конкурирующий процесс уже создал диалог
                    select @Handle      = CEP.conversation_handle
                    from   sys.conversation_endpoints CEP
                    where  CEP.far_service = 'EventService'
                                  and CEP.state = 'CO'
                                  and CEP.is_initiator = 1
 
                    if     @Handle      is null
                           begin dialog conversation @Handle
                           from service EventService to service 'EventService', 'current database'
                           with encryption = off;
             end
 
             ;send on conversation @Handle (@Event)
 
       commit

			set	@Text = (
				select	*
				from	sys.conversation_endpoints CEP with(nolock)
				for xml path('dialogs')
			)