How do I parse a string with a decimal point to a double?

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I want to parse a string like "3.5" to a double. However, 

double.Parse("3.5")

yields 35 and 

double.Parse("3.5", System.Globalization.NumberStyles.AllowDecimalPoint)

throws a FormatException.

Now my computer's locale is set to German, wherein a comma is used as decimal separator. It might have to do something with that and double.Parse() expecting "3,5" as input, but I'm not sure.

How can I parse a string containing a decimal number that may or may not be formatted as specified in my current locale?

double parsing string c#
18 Answers

My two cents on this topic, trying to provide a generic, double conversion method:

private static double ParseDouble(object value)
{
    double result;

    string doubleAsString = value.ToString();
    IEnumerable<char> doubleAsCharList = doubleAsString.ToList();

    if (doubleAsCharList.Where(ch => ch == '.' || ch == ',').Count() <= 1)
    {
        double.TryParse(doubleAsString.Replace(',', '.'),
            System.Globalization.NumberStyles.Any,
            CultureInfo.InvariantCulture,
            out result);
    }
    else
    {
        if (doubleAsCharList.Where(ch => ch == '.').Count() <= 1
            && doubleAsCharList.Where(ch => ch == ',').Count() > 1)
        {
            double.TryParse(doubleAsString.Replace(",", string.Empty),
                System.Globalization.NumberStyles.Any,
                CultureInfo.InvariantCulture,
                out result);
        }
        else if (doubleAsCharList.Where(ch => ch == ',').Count() <= 1
            && doubleAsCharList.Where(ch => ch == '.').Count() > 1)
        {
            double.TryParse(doubleAsString.Replace(".", string.Empty).Replace(',', '.'),
                System.Globalization.NumberStyles.Any,
                CultureInfo.InvariantCulture,
                out result);
        }
        else
        {
            throw new ParsingException($"Error parsing {doubleAsString} as double, try removing thousand separators (if any)");
        }
    }

    return result;
}

Works as expected with:

  • 1.1
  • 1,1
  • 1,000,000,000
  • 1.000.000.000
  • 1,000,000,000.99
  • 1.000.000.000,99
  • 5,000,111.3
  • 5.000.111,3
  • 0.99,000,111,88
  • 0,99.000.111.88

No default conversion is implemented, so it would fail trying to parse 1.3,14, 1,3.14 or similar cases.

user_54593210 
        var doublePattern = @"(?<integer>[0-9]+)(?:\,|\.)(?<fraction>[0-9]+)";
        var sourceDoubleString = "03444,44426";
        var match = Regex.Match(sourceDoubleString, doublePattern);

        var doubleResult = match.Success ? double.Parse(match.Groups["integer"].Value) + (match.Groups["fraction"].Value == null ? 0 : double.Parse(match.Groups["fraction"].Value) / Math.Pow(10, match.Groups["fraction"].Value.Length)): 0;
        Console.WriteLine("Double of string '{0}' is {1}", sourceDoubleString, doubleResult);
user_2082720

Here is a solution that handles any number string that many include commas and periods. This solution is particular for money amounts so only the tenths and hundredths place are expected. Anything more is treated as a whole number.

First remove anything that is not a number, comma, period, or negative sign.

string stringAmount = Regex.Replace(originalString, @"[^0-9\.\-,]", "");

Then we split up the number into the whole number and decimal number.

string[] decimalParsed = Regex.Split(stringAmount, @"(?:\.|,)(?=\d{2}$)");

(This Regex expression selects a comma or period that is two numbers from the end of the string.)

Now we take the whole number and strip it of any commas and periods.

string wholeAmount = decimalParsed[0].Replace(",", "").Replace(".", "");

if (wholeAmount.IsNullOrEmpty())
        wholeAmount = "0";

Now we handle the decimal part, if any.

string decimalAmount = "00";

if (decimalParsed.Length == 2)
    {
        decimalAmount = decimalParsed[1];
    }

Finally we can put the whole and decimal together and parse the Double.

double amount = $"{wholeAmount}.{decimalAmount}".ToDouble();

This will handle 200,00, 1 000,00 , 1,000 , 1.000,33 , 2,000.000,78 etc.

user_60584120
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