Double to string conversion without scientific notation

Question

How to convert a double into a floating-point string representation without scientific notation in the .NET Framework?

\"Small\" samples (effective numbers may be of

Answer 1

This is what I've got so far, seems to work, but maybe someone has a better solution:

private static readonly Regex rxScientific = new Regex(@"^(?-?)(?\d+)(\.(?\d*?)0*)?E(?[+\-]\d+)$", RegexOptions.IgnoreCase|RegexOptions.ExplicitCapture|RegexOptions.CultureInvariant);

public static string ToFloatingPointString(double value) {
    return ToFloatingPointString(value, NumberFormatInfo.CurrentInfo);
}

public static string ToFloatingPointString(double value, NumberFormatInfo formatInfo) {
    string result = value.ToString("r", NumberFormatInfo.InvariantInfo);
    Match match = rxScientific.Match(result);
    if (match.Success) {
        Debug.WriteLine("Found scientific format: {0} => [{1}] [{2}] [{3}] [{4}]", result, match.Groups["sign"], match.Groups["head"], match.Groups["tail"], match.Groups["exponent"]);
        int exponent = int.Parse(match.Groups["exponent"].Value, NumberStyles.Integer, NumberFormatInfo.InvariantInfo);
        StringBuilder builder = new StringBuilder(result.Length+Math.Abs(exponent));
        builder.Append(match.Groups["sign"].Value);
        if (exponent >= 0) {
            builder.Append(match.Groups["head"].Value);
            string tail = match.Groups["tail"].Value;
            if (exponent < tail.Length) {
                builder.Append(tail, 0, exponent);
                builder.Append(formatInfo.NumberDecimalSeparator);
                builder.Append(tail, exponent, tail.Length-exponent);
            } else {
                builder.Append(tail);
                builder.Append('0', exponent-tail.Length);
            }
        } else {
            builder.Append('0');
            builder.Append(formatInfo.NumberDecimalSeparator);
            builder.Append('0', (-exponent)-1);
            builder.Append(match.Groups["head"].Value);
            builder.Append(match.Groups["tail"].Value);
        }
        result = builder.ToString();
    }
    return result;
}

// test code
double x = 1.0;
for (int i = 0; i < 200; i++) {
    x /= 10;
}
Console.WriteLine(x);
Console.WriteLine(ToFloatingPointString(x));