C# : Some basic validation

Doing some basic validation and I found these to be useful:

Check for mandatory fields:
if (String.IsNullOrEmpty (xxx)) … error

Field must be numeric only:
int number;
bool result = Int32.TryParse (xxx, out number);
if (!result) … error

Valid date format:
DateTime date;
bool result = DateTime.TryParse (xxx, out date);
if (!result) … error

Valid email format:
bool result = Regex.IsMatch(xxx, @"^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)
(([\w-]+\.)+))([a-zA-Z]{2,4}[0-9]{1,3})(\]?)$");
if (!result) … error

Enjoy!