Hi Praveen,
If you want to do it in asp.net then you can refer
here[
^]
If you want to check it in DB side then you can use
EXISTS
function like this
IF NOT EXISTS(SELECT ID FROM InsertTableName WHERE ID = 'ID you want to insert')
BEGIN
INSERT INTO InsertTableName VALUES(101,'Name');
ELSE
Print 'Record already exist'
Hope this helps you a bit.
Regards,
RK