How to mask string?

Question

I have a string with value "1131200001103".

How can I display it as a string in this format "11-312-001103" using Response.Write(value)?

Thanks

Answer 1

I wrote a quick extension method for same / similar purpose (similar in a sense that there's no way to skip characters).

Usage:

var testString = "12345";
var maskedString = testString.Mask("##.## #"); // 12.34 5

Method:

public static string Mask(this string value, string mask, char substituteChar = '#')
{
    int valueIndex = 0;
    try
    {
        return new string(mask.Select(maskChar => maskChar == substituteChar ? value[valueIndex++] : maskChar).ToArray());
    }
    catch (IndexOutOfRangeException e)
    {
        throw new Exception("Value too short to substitute all substitute characters in the mask", e);
    }
}

Answer 2

Any reason you don't want to just use Substring?

string dashed = text.Substring(0, 2) + "-" +
                text.Substring(2, 3) + "-" +
                text.Substring(7);

Or:

string dashed = string.Format("{0}-{1}-{2}", text.Substring(0, 2),
                              text.Substring(2, 3), text.Substring(7));

(I'm assuming it's deliberate that you've missed out two of the 0s? It's not clear which 0s, admittedly...)

Obviously you should validate that the string is the right length first...