Hello what is the meaning of this error? The operation + cannot accept the arguments

Do you have any number in StationBooking.Text and StationPassenger.Text and other two?
Empty string can not be used for math caculation.


GetValue will not fire DataChanged event.

And you need to make all the Label (or Textbox) have a number when caculation.

thank you sir i get it..

Dear @kevin ,
I'm not so familiar with firebase, but it seems that you look for tags without colon ":" while the tag is with ":"
Could it be that the reason why the GetValue returns empty strings ?