how to get total days in from selected date to till Date

Question

Hi

I have a form in that form there are 3 fields

 

1) From             DateTimePicker   

2) To                 DateTimePicker   

2) Total days     textbox

 

when I choose any of the date From DateTimePicker   and To DateTimePicker   

I want the total days in the textbox

 

how I can do it please help me