Format a Social Security Number (SSN) as XXX-XX-XXXX from XXXXXXXXX

问题

I am getting a social security number (SSN) from a data warehouse. While posting it to a CRM I want it to be formatted like XXX-XX-XXXX instead of XXXXXXXXX.

It's like converting a simple string with dashes at positions 4 and 7. I am pretty new to C#, so what is the best way to do this?

回答1:

Check out the String.Insert method.

string formattedSSN = unformattedSSN.Insert(5, "-").Insert(3, "-");

回答2:

For a simple, short, and self commenting solution, try:

String.Format("{0:000-00-0000}", 123456789)

123456789 representing your SSN variable.

回答3:

string ssn = "123456789";

string formattedSSN = string.Join("-", 
                                  ssn.Substring(0,3), 
                                  ssn.Substring(4,2), 
                                  ssn.Substring(6,4));

@George's option is probably cleaner if the SSN is stored as a numeric rather than as a string.

回答4:

Just in case this helps someone, here is a method I created to mask and format a SSN:

USAGE:

string ssn = "123456789";
string masked = MaskSsn(ssn); // returns xxx-xx-6789

CODE:

public static string MaskSsn(string ssn, int digitsToShow = 4, char maskCharacter = 'x')
{
    if (String.IsNullOrWhiteSpace(ssn)) return String.Empty;

    const int ssnLength = 9;
    const string separator = "-";
    int maskLength = ssnLength - digitsToShow;

    // truncate and convert to number
    int output = Int32.Parse(ssn.Replace(separator, String.Empty).Substring(maskLength, digitsToShow));

    string format = String.Empty;
    for (int i = 0; i < maskLength; i++) format += maskCharacter;
    for (int i = 0; i < digitsToShow; i++) format += "0";

    format = format.Insert(3, separator).Insert(6, separator);
    format = "{0:" + format + "}";

    return String.Format(format, output);
}

回答5:

Without data validation and assuming that you only get 9 character string, I would go with something like this -

return s.Substring(0, 3) + "-" + s.Substring(3, 2) + "-" + s.Substring(5, 4);

But...I am also pretty new...so GendoIkari's answer is soo much better.

回答6:

Above answer might be raise exception when string not fixed length.

In my case I used following way SSN formating and its working.

string SSN = "56245789";
if (SSN.Length > 3 && SSN <= 5)
      SSN = SSN.Insert(3, "-");
else if (SSN.Length > 5)
      SSN = SSN.Insert(5, "-").Insert(3, "-");

Hence SSN will get 562-45-789.

来源：https://stackoverflow.com/questions/4128263/format-a-social-security-number-ssn-as-xxx-xx-xxxx-from-xxxxxxxxx

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