How to give user defined validation in asp.net?
<p>I have a grid to which there are edit/delete/insert buttons, there is a column in the grid say  SR_NO ,the user can simply add a number in this field and append/edit to the grid.</p>

<p>but the thing is I want to validate this field such that there is no other entry in the entire SR_NO column having same SR_NO,how can do this?</p>

<p>The only validations I have used till now are required field and reg-ex format validator ,so little dim on this aspect  please help....</p>
