title: How to Update a textbox with a value from another textbox?
body: <p>I have two <code>textboxes</code> named <code>totalAmount</code> and <code>expenseAmount</code> and another a <code>div</code> called <code>currentAmount</code> in asp.net page(using C#).
  My requirement is I have to update <code>totalAmount=expenseAmount+currentAmount</code> whenever <code>expenseAmount</code> value changes.I have to achieve this without page refresh and value should be persist even after page refresh.</p>