Function for Email Validation 1. It allows max 5 dots(.) including .com and max 5 hyphen(-) 2. Only 4 Special Characters allowed are (- _ . @) 3. @ character is allowed only once and is mandatory. private bool email() { string pattern = @"^([a-zA-Z0-9])+([\w_\.\-]([a-zA-Z0-9])*[a-zA-Z0-9])*@([a-zA-Z0-9_\-\.]+)\.([a-zA-Z]{2,5}$)"; System.Text.RegularExpressions.Match match = Regex.Match(textBox1.Text.Trim(), pattern, RegexOptions.IgnoreCase); if ((match.Success)) { string[] words = Regex.Split(textBox1.Text.Trim(), "@"); string word1 = words[1].ToString(); int dotCount = word1.Count(f = > f == '.'); int hyfenCount = word1.Count(f = > f == '-'); if (!(dotCount < 6)) { MessageBox.Show("Invalid Email-id"); return false; } else if (!(h