Unconsistence NumericUpDown Control [Resolved]

I use a NumericUpDown control to let user set the "birth date year" value.
the max value of NumericUpDownYear is 2002, while min value is 1880
whenever the value of this control changed, the txtAge textbox will generate the age value:
txtAge.Text = System.DateTime.Today.Year - NumericUpDownYear.Text
but it seems to be not consistant at all. because the age that being generated is not correct n different all the time.
what do i need to do now to make it consistence all the time?
Please help. 10q!

use NumericUpDownYear.Value instead of NumericUpDownYear.Text. See if it helps.

Thanks for your guidance, NumericUpDownYear.Value works exactly now!