NumericUpDown is an ASP.NET AJAX extender that can be attached to an ASP.NET TextBox control to add the up and down buttons that increment and decrement a value in the TextBox. The increment and decrement actions can be simple +1/-1 arithmetic, cycle through the provided list of values (like months of the year), or call a Web Service to determine the next value. Page authors can also provide custom images to be used instead of the default up/down button graphics.