title: How to key trap in C#?
body: <p>i am just a newbie in programming. i want to know on how to key trap a letter or a number in a text box. example, there is a text box about age, the user will not type a letter on that text box. And also, i want to know how to limit number of characters that will enter on that text box. example, there is a text box about grades, the user cannot type 1111 on grades. I am using c#, asp.net and sql server 2008 for database. an example is enough for me. thanks</p>