Last Four Digit of SSN(Social Security Number).

For Security purpose,we also have to hide SSN number or Masked
Below property will be used for masking first 5 digit of SSN as X and showing Last four digit.

public string LAST_FOUR_DIGIT_SSN
{
  get
  {
     string LastFourDigitSSN = ssn.Substring(5, 4);
     return "XXX-XX-" + LastFourDigitSSN;
  }
}

Use it any where on the page.