String Extension improvement

Question

I am creating a string extension to validate some input.

My scenario is when we have a string it will format it according to following guideline. If the sample string is “One Two Three Four Five” and the length is <=20 return same. If more than 20 then “One Two Three F Five”. If still length is more than 20 the “One Two T F Five” etc...

Is there any way I can improve this code? I thought it can use recursion?

public static string ToShortName(this string name)
        {
            if (name.Length <= 20) return name;

            var namelist = name.Split(' ');

            var length = name.Length;

            //add spaces
            length = length + namelist.Count() - 1;

            var output = "";
            var indexList = new List<int>();
            for (var i = namelist.Count() - 2; i >=1 ; i--)
            {
                indexList.Add(i);
                if (length - namelist[i].Length <= 20)
                {
                    break;
                }
                length = length - namelist[i].Length;
            }

            foreach (var i in indexList)
            {
                namelist[i] = namelist[i].Substring(0, 1);
            }
            output = string.Join(" ", namelist);

            return output;
        }

Answer 1

You should remove this

length = length + namelist.Count() - 1;

because length already includes the spaces.

This

length = length - namelist[i].Length;

should be

length -= namelist[i].Length - 1;

because namelist[i].Length-1 is the number of characters that are removed.

Also: why i >=1 - 1 instead of i >= 0?

You can also do it in a single loop like this:

        for (var i = namelist.Count() - 2; i >=1 && length > 20; i--)
        {
            length -= namelist[i].Length - 1;
            namelist[i] = namelist[i].Substring(0, 1);
        }

        return string.Join(" ", namelist);

Answer 2

public static string StringCorrection(this string name)

StringCorrection() is not a great name. 1. I don't see any reason to call out the String type in the name. 2. This is not really a correction, it's more like shortening.

Also, I'm not sure that this should be an extension method, because it's something quite specific, it's not generally useful for almost any string.

if (name.Length <= 20) return name;

I think the max length should be a parameter with a default value, so that the method is more general. Even if you don't do that, at least don't repeat the value, use a variable for it.

var output = "";

There doesn't seem to be any reason to declare the variable this early, or to actually have the variable at all. You could just write:

return string.Join(" ", namelist);

Answer 3

Here is more concise implementation. Also, when length of the string is more than max length, we need to run the loop at least once, so we should use do..while here.

public static string StringCorrection(this string name)
{
    int maxLength = 20;
    if (name.Length <= maxLength) return name;

    string[] nameArray = name.Split(' ');
    int extraLength = name.Length - maxLength;
    int currentIndex = nameArray.Length - 2;

    if (currentIndex <= 0) return name;

    int wordLength = 0;
    do
    {
        wordLength = nameArray[currentIndex].Length;
        nameArray[currentIndex] = nameArray[currentIndex].Substring(0, 1);
        extraLength -= (--wordLength);
        currentIndex--;
    } while (extraLength > 0 && currentIndex > 0);

    return string.Join(" ", nameArray);
}