Extension method to add ellipsis at the end of a string if it is too big.

StringExtensions.cs

private const string EllipsisString = "…";
public static string Ellipsis(this string str, int maxChars, bool breakOnNewLine = false) {
    if (maxChars < 1) {
        throw new ArgumentOutOfRangeException(nameof(maxChars), "maxChars must be 1 or more.");
    }
    string changed = str;
    if (breakOnNewLine) {
        int newLine = changed.IndexOf('\n');
        if (newLine > -1) {
            changed = changed.Substring(0, newLine) + EllipsisString;
        }
    }
    if (changed.Length > maxChars) {
        int lastWordBoundaryInRange = changed.LastIndexOf(' ', maxChars) - 1;
        if (lastWordBoundaryInRange < 0) {
            lastWordBoundaryInRange = maxChars -1;
        }
        changed = changed.Substring(0, lastWordBoundaryInRange);
        changed = changed.TrimEnd() + EllipsisString;
    }
    return changed;
}