title: BotFramework 1:1 conversation throws error "activityid can not be null"
body: <p>While trying to create a 1:1 conversation using the following code, I get the error saying "activityid cannot be null" can someone please help me pointing out what is wrong? </p>
  
  <pre><code> var newRecipient = new ChannelAccount();
                              newRecipient.Name = user.Mentioned.Name;
                              newRecipient.Id = user.Mentioned.Id;
  
                              var ConversationId = await connector.Conversations.CreateDirectConversationAsync(activity.Recipient, newRecipient);
                              IMessageActivity message = Activity.CreateMessageActivity();
                              message.From = activity.Recipient;
                              message.Recipient = newRecipient;
                              message.Conversation = new ConversationAccount(id: ConversationId.Id);
                              message.Text = $"Congratulations {user.Mentioned.Name}!, you have got a :tangerine: from {activity.From.Name}";
                              message.Locale = "en-Us";
                              message.Id = Guid.NewGuid().ToString(); 
                              var reply = await connector.Conversations.ReplyToActivityAsync((Activity)message);
  </code></pre>