Your need is not looks like valid because if u wnat avoid client side validation thats ok , u don't use javascript validation u use server side valudation in C#.net this is significante but u don't wnat to use regular expression this doesn't have any significante because in C#.net u must use expression for validation email as
public static bool isEmail(string inputEmail)
{
inputEmail = NulltoString(inputEmail);
string strRegex = @"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}" +
@"\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\" +
@".)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$";
Regex re = new Regex(strRegex);
if (re.IsMatch(inputEmail))
return (true);
else
return (false);
}
this is alos use regular expression but no need to validation control.
hope this helps u