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stewartrae on 05/24/11

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extension
c#

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Last Edited at 05/24/11 05:02pm

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TruncateOnWordBoundary - a useful extension method for cutting a string short, but not in the middle of a word.

/ Published in: C#

Ever wanted a method that can truncate a string, but only on a word boundary? This method works like Substring() but doesn't snip a string in the middle of a word, i.e. it only truncates the string on a word boundary. Useful for producing a summary from long text, or when limiting the length of an input field.

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/// <summary>
/// String extension methods.
/// </summary>
public static class StringExtension
{
    private const string ellipsis = "...";
 
    /// <summary>
    /// Truncates the supplied content to the max length on a word boundary and adds an ellipsis if longer.
    /// </summary>
    /// <param name="content">The string to truncate</param>
    /// <param name="maxLength">Max number of characters to show, not including continuation content</param>
    /// <returns>The truncated string</returns>
    public static string TruncateOnWordBoundary(this string content, int maxLength)
    {
        return content.TruncateOnWordBoundary(maxLength, ellipsis);
    }
 
    /// <summary>
    /// Truncates the supplied content to the max length on a word boundary and adds the suffix if longer.
    /// </summary>
    /// <param name="content">The string to truncate</param>
    /// <param name="maxLength">Max number of characters to show, not including the suffix</param>
    /// <param name="suffix">Suffix to append if content is truncated</param>
    /// <returns>The truncated string</returns>
    public static string TruncateOnWordBoundary(this string content, int maxLength, string suffix)
    {
        // No content? Return an empty string.
        if (String.IsNullOrEmpty(content))
            return String.Empty;
 
        // Content is shorter than the max length? Return the whole string.
        if (content.Length < maxLength)
            return content;
 
        // Find the word boundary.
        int i = maxLength;
        while (i > 0)
        {
            if (Char.IsWhiteSpace(content[i]))
                break;
            i--;
        }
 
        // Can't truncate on a word boundary? Just return the suffix, e.g. "...".
        if (i <= 0)
            return (suffix ?? ellipsis); // Just in case a null suffix was supplied.
 
        return content.Substring(0, i) + (suffix ?? ellipsis);
    }
}