About Upper case letters or Lower case letters Password ?

Try this:
string password= "USERS";
bool result = password.Equals(textbox.Text, StringComparison.Ordinal);

based on this bool variable, you can take your decision whether to allow login or not. Hope it answered your query.

yes

i was created a registration page i.e., username and password....
but when iam using password.. i gave upper case alphabet letters. but..., when i enter lower case letters also it is opening....  in that registration page how can write code... plz help me.

Chinna Netha,
Are you looking for case-sensitive comparison ?

Hi chinna Netha.

plz share you code, without code i can't understand.