Select all numbers from textfield seperated by comma for send sms in c#

string csv = txt.Text.Trim();
           string[] phoneNumbers = csv.Split(',');
           var validNumbers = phoneNumbers.Where(k => k.Length == 10).ToArray(); // this array has valid numbers
           var invalidNumbers = phoneNumbers.Where(k => k.Length != 10).ToArray(); // this array has invalid numbers 


 foreach (string _phoneNumber in validNumbers)
           {
               // sendSMS ( _phoneNumber );
           }