NexusSmallErp: CsharpRegex ...

// Replace invalid characters with empty strings.

//return Regex. Replace(strIn, @"[^\w\.@-]", );

String lxm = strIn;
Regex rx005 = new Regex(@"^(\r\n)"); // empty string at the beginning
Regex rx004 = new Regex(@"(\r\n)\1"); // empty string
Regex rx003 = new Regex(@"( \r\n)"); // empty string with space
Regex rx002 = new Regex(@"([ ])\1"); // many space moving to space
Regex rx001 = new Regex(@"([\t])"); // tab moving to space

// tab moving to space
do { lxm = rx001.Replace(lxm, " "); } while (rx001.IsMatch(lxm) == true);

// many space moving to space
do { lxm = rx002.Replace(lxm, " "); } while (rx002.IsMatch(lxm) == true);

// empty string with space
do { lxm = rx003.Replace(lxm, "\r\n"); } while (rx003.IsMatch(lxm) == true);

// empty string
do { lxm = rx004.Replace(lxm, "\r\n"); } while (rx004.IsMatch(lxm) == true);

lxm = rx005.Replace(lxm, );

//result back
return lxm;