PaddedStringFormatInfo

public sealed class PaddedStringFormatInfo : IFormatProvider, ICustomFormatter {
    public object GetFormat(Type formatType)
    {
        if (typeof(ICustomFormatter).Equals(formatType)) return this;
        return null;
    }

    public string Format(string format, object arg, IFormatProvider formatProvider)
    {
        if (arg == null)
            throw new ArgumentNullException("Argument cannot be null");

        string[] args;
        if (format != null)
            args = format.Split(':');
        else
            return arg.ToString();

        if (args.Length == 1)
            String.Format("{0, " + format + "}", arg);

        int padLength = 0;

        if (!int.TryParse(args[0], out padLength))
            throw new ArgumentException("Padding lenght should be an integer");
        switch (args.Length)
        {
            case 2://Padded format
                if (padLength > 0)
                    return (arg as string).PadLeft(padLength, args[1][0]);
                return (arg as string).PadRight(padLength * -1, args[1][0]);
            default://Use default string.format
                return string.Format("{0," + format + "}", arg);
        }
    }
}