Truncate string on whole words in .NET C#

Question

I am trying to truncate some long text in C#, but I don\'t want my string to be cut off part way through a word. Does anyone have a function that I can use to truncate my st

Answer 1

Taking into account more than just a blank space separator (e.g. words can be separated by periods followed by newlines, followed by tabs, etc.), and several other edge cases, here is an appropriate extension method:

    public static string GetMaxWords(this string input, int maxWords, string truncateWith = "...", string additionalSeparators = ",-_:")
    {
        int words = 1;
        bool IsSeparator(char c) => Char.IsSeparator(c) || additionalSeparators.Contains(c);

        IEnumerable<char> IterateChars()
        {
            yield return input[0];

            for (int i = 1; i < input.Length; i++)
            {
                if (IsSeparator(input[i]) && !IsSeparator(input[i - 1]))
                    if (words == maxWords)
                    {
                        foreach (char c in truncateWith)
                            yield return c;

                        break;
                    }
                    else
                        words++;

                yield return input[i];
            }
        }

        return !input.IsNullOrEmpty()
            ? new String(IterateChars().ToArray())
            : String.Empty;
    }

Answer 2

simplified, added trunking character option and made it an extension.

    public static string TruncateAtWord(this string value, int maxLength)
    {
        if (value == null || value.Trim().Length <= maxLength)
            return value;

        string ellipse = "...";
        char[] truncateChars = new char[] { ' ', ',' };
        int index = value.Trim().LastIndexOfAny(truncateChars);

        while ((index + ellipse.Length) > maxLength)
            index = value.Substring(0, index).Trim().LastIndexOfAny(truncateChars);

        if (index > 0)
            return value.Substring(0, index) + ellipse;

        return value.Substring(0, maxLength - ellipse.Length) + ellipse;
    }

Answer 3

This solution works too (takes first 10 words from myString):

String.Join(" ", myString.Split(' ').Take(10))

Answer 4

My contribution:

public static string TruncateAtWord(string text, int maxCharacters, string trailingStringIfTextCut = "…")
{
    if (text == null || (text = text.Trim()).Length <= maxCharacters) 
      return text;

    int trailLength = trailingStringIfTextCut.StartsWith("&") ? 1 
                                                              : trailingStringIfTextCut.Length; 
    maxCharacters = maxCharacters - trailLength >= 0 ? maxCharacters - trailLength 
                                                     : 0;
    int pos = text.LastIndexOf(" ", maxCharacters);
    if (pos >= 0)
        return text.Substring(0, pos) + trailingStringIfTextCut;

    return string.Empty;
}

This is what I use in my projects, with optional trailing. Text will never exceed the maxCharacters + trailing text length.