How can I use placeholders for characters in a string?

Question

I am trying to use the solution provided in this answer, and have also referenced this article.

Basically, I am trying to format a social security number. This is the method used in the articles linked above:

String.Format(“{0:###-##-####}”, 123456789);

This works great when the number is passed in as shown above, but the number I need to format is contained in a string - so I am essentially doing this (which doesn't work):

String.Format(“{0:###-##-####}”, "123456789");

What is a good way to get around my problem?

score 3 · Accepted Answer · answered Mar 24 '14 at 15:08

3

You can parse the string to numeric type and then use string.Format like:

String.Format("{0:###-##-####}", long.Parse("123456789"));

You can also use long.TryParse or int.TryParse based on your number, and then use that value in string.Format.

long number;
string str = "123456789";
if (!long.TryParse(str, out number))
{
    //invalid number
}

string formattedStr = String.Format("{0:###-##-####}", number);

answered Mar 24 '14 at 15:08

Habib

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What if the SSN has letters? – Lews Therin Mar 24 '14 at 15:09
How do you know it is SSN ? – Habib Mar 24 '14 at 15:09
I am not sure if that's a relevant use case though. – Lews Therin Mar 24 '14 at 15:09
2

"Basically, I am trying to format a social security number." – Lews Therin Mar 24 '14 at 15:10
@LewsTherin, I missed that, but if the OP is trying to format the SSN, then I can only assume that it is number and it requires formatting, if it is already formatted, then there is no point in using `String.Format` – Habib Mar 24 '14 at 15:12

score 1 · Answer 2 · answered Mar 24 '14 at 15:24

1

You can use Regex.Replace method

string formatted = Regex.Replace("123456789", @"(.{3})(.{2})(.{4})", "$1-$2-$3");

Given you have not so many digits (or letters), you can use multiple dots.

string formatted = Regex.Replace("123456789", @"(...)(..)(....)", "$1-$2-$3");

answered Mar 24 '14 at 15:24

Ulugbek Umirov

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Yes, It works even if the number consists of a mix of letters and digits. – Olivier Jacot-Descombes Mar 24 '14 at 15:28

score 0 · Answer 3 · answered Mar 24 '14 at 15:16

0

You can try to print single character

 string.Format("{0}{1}{2}", "123".ToCharArray().Cast<object>().ToArray())

Modify this code to support variable length of SSN (if it's necessary - build format string in runtime).

answered Mar 24 '14 at 15:16

lavrik

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score 0 · Answer 4 · answered Mar 24 '14 at 15:19

SSN are normally stored in varchar. If so, you can use like this utility method.

public static string FormatSSN(string ssn)
{
    if (String.IsNullOrEmpty(ssn))
        return string.Empty;

    if (ssn.Length != 9)
        return ssn;

    string first3 = ssn.Substring(0, 3);
    string middle2 = ssn.Substring(6, 2);
    string last4 = ssn.Substring(5, 4);

    return string.Format("{0}-{1}-{2}", first3, middle2, last4);
}

How can I use placeholders for characters in a string?

4 Answers4