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

Question

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?

Solution 1

Check out the String.Insert method.

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

Solution 2

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

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

123456789 representing your SSN variable.

Solution 3

string ssn = "123456789";

string formattedSSN = string.Join("-", 
                                  ssn.Substring(0,3), 
                                  ssn.Substring(3,2), 
                                  ssn.Substring(5,4));

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

start indexes corrected.

Solution 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);
}

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Comments

[GendoIkari]

You have an extra # in the middle. Other than that, +1 because it's much more elegant than my solution.

[tnyfst]

Close, but you need "{0:000-00-0000}" instead of '#' to allow for leading zeroes (or "{0:00#-##-####}" etc.).

[wageoghe]

Tricky. It is interesting to note that the "obvious" answer of doing it like this (note my reversal of 3 and 5 compared to yours): unformattedSSN.Insert(3,"-").Insert(5,"-"); would yield 123-4-56789 rather than 123-45-6789. So, you are, in effect inserting dashes from back to front.

[GendoIkari]

Yeah, you could do it forwards instead of backwards, but then you'd have to account for the extra dash that you inserted.

[Peter M]

You are assuming that the data is coming in a numeric form. I am not sure how SSN data is typically kept but I would have expected a 9 character string rather than a numerical value given the specification for the first 3 chars includes leading zeroes. If the former then you would need to add in a string->numeric conversion (or is there an implicit one?).

[GendoIkari]

Why was this downvoted a month and a half after it was accepted?

[David Heffernan]

@Gendolkari This is a fine example of a situation where a fluent interface is poor. As you have acknowledged, George's solution is clearer and easier to verify.

[mdelvecchio]

George's solution fails when the SSN is stored as a string, which is specified in the question.

[mdelvecchio]

yeah this fails -- the question specifies the SSN value is a string, and this solution will not work on a string.

[Casey]

@mdelvecchio Never mind correctness -- being easier to read is clearly a greater virtue than actually solving the problem.

[mdelvecchio]

@Casey no, SO is all about accuracy in answers. that's why we're here. as for this problem, the SSN is a string, thus George's answer won't work since its for a numeric data type. change the question if you like, but numeric is a different problem than string.

[GendoIkari]

@mdelvecchio I could be wrong, but I'm pretty sure Casey was being sarcastic and agreeing with you.

[Casey]

@GendoIkari That was, indeed, what I meant.

[mdelvecchio]

ah..missed it for some reason last nite, sorry. /s tag helps tho!

[Anthony Nichols]

This isn't a good solution - SSNs should never be stored as a number because they can start with a 0. This only works for formatting a number. The accepted answer is the right answer.

[GendoIkari]

@Ch'nycos Then this would throw a runtime error. There are plenty of ways to avoid this; but I think it's outside the scope of the question.