What's the most efficient way to format the following string?

Question

I have a very simple question, and I shouldn't be hung up on this, but I am. Haha!

I have a string that I receive in the following format(s):

123

123456-D53

123455-4D

234234-4

123415

The desired output, post formatting, is:

123-455-444

123-455-55

123-455-5

or

123-455

The format is ultimately dependent upon the total number of characters in the original string..

I have several ideas of how to do this, but I keep thing there's a better way than string.Replace and concatenate...

Thanks for the suggestions..

Ian

Answer 1

Tanascius is right but I cant comment or upvote due to my lack of rep but if you want additional info on the string.format Ive found this helpful. http://blog.stevex.net/string-formatting-in-csharp/

Answer 2

I assume this does not merely rely upon the inputs always being numeric? If so, I'm thinking of something like this

private string ApplyCustomFormat(string input)
{
    StringBuilder builder = new StringBuilder(input.Replace("-", ""));

    int index = 3;
    while (index < builder.Length)
    {
        builder.Insert(index, "-");
        index += 4;
    }
    return builder.ToString();
}