Following regular expression
can be used to check that email id is in correct format or not.
string
strEmail = "test1test.com";
Regex
regex = new Regex(@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*");
if
(!regex.IsMatch(strEmail))
{
return "Email id
is not in correct format";
}