CODEWITHSUNDEEP
c#decimaltryparseregional-settings
ng80092b
ng80092b

Reputation: 667

Make TryParse compatible with comma or dot decimal separator

The problem: Let's assume you are using a dot "." as a decimal separator in your regional setting and have coded a string with a comma.

string str = "2,5";

What happens when you decimal.TryParse(str, out somevariable); it?

somevariable will assume 0.

What can you do to solve it?

1- You can 

decimal.TryParse(str, NumberStyles.Any, CultureInfo.InvariantCulture, out somevariable);

And it will return 25, and not 2.5 which is wrong.

2- You can 

decimal.TryParse(str.Replace(",","."), out num);

And it will return the proper value, BUT, if the user uses "," as a decimal separator it will not work.

Possible solution that I can't make it work:

Get the user decimal separator in regional settings:

char sepdec = Convert.ToChar(CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator);

And make somehow the replace from ",",sepdec , that way it would stay a comma if its a comma, and replace by an actual dot if the user uses dots.

Hints?

Edit: Many users posted useful information, lately, using the arguments NumberStyles.Any, CultureInfo.GetCultureInfo("pt-PT") on a tryParse wouldn't work if your separator is set to "," So it pretty much doesnt fullfill the premise of making a tryparse "universal".

I'll work around this, if anyone has more hints you'r welcome

Upvotes: 30

Views: 37025

Answers (7)

Jonny
Jonny

Reputation: 1161

The question is old but since it was my first hit on Google. And the approach in How to change symbol for decimal point in double.ToString()? seems to be a valid solution you can use the NumberFormatInfo to set the decimal separator like this:

string value = "3,2";
NumberFormatInfo nfi = new NumberFormatInfo();
nfi.NumberDecimalSeparator = ",";

decimal.TryParse(value, NumberStyles.Any, nfi, out decimal dec);

Upvotes: 3

Adrian
Adrian

Reputation: 23

I just want to say that HTH Thomas solution worked really well in my project, except for when trying to parse negative decimal numbers with commas. One solution to this, which is probably not optimized because I don't fully understand the regex Ismatch code, but that works is adding the possibility of finding a "-" before the number in the ifs statements, like this:

        var cultureInfo = CultureInfo.InvariantCulture;
        if (Regex.IsMatch(equation.inputFieldsTexts[i], @"^(:?[\d,]+\.)*\d+$") || Regex.IsMatch(equation.inputFieldsTexts[i], @"^(:?[-\d,]+\.)*\d+$"))
        {
            cultureInfo = new CultureInfo("en-US");
        }
        // if the second regex matches, the number string is in DE culture
        if (Regex.IsMatch(equation.inputFieldsTexts[i], @"^(:?[\d.]+,)*\d+$") || Regex.IsMatch(equation.inputFieldsTexts[i], @"^(:?[-\d.]+,)*\d+$"))
        {
            cultureInfo = new CultureInfo("de-DE");
        }

Upvotes: 1

MartinHoly
MartinHoly

Reputation: 167

How about this method:

  • clean the string from anything else than numbers, dot, comma and negative sign
  • take the last index of dot or comma
  • split the clean string and remove all thousands separators from the first part
  • convert both parts to integer
  • change the sign of the second part if necessary
  • add the first part with the second part divided by decimal places
public static bool TryParseDoubleUniversal(this string s, out double result) {
  result = 0.0;
  if (string.IsNullOrEmpty(s)) return false;

  var clean = new string(s.Where(x => char.IsDigit(x) || x == '.' || x == ',' || x == '-').ToArray());
  var iOfSep = clean.LastIndexOfAny(new[] { ',', '.' });
  var partA = clean.Substring(0, iOfSep).Replace(",", string.Empty).Replace(".", string.Empty);
  var partB = clean.Substring(iOfSep + 1);
  if (!int.TryParse(partA, out var intA)) return false;
  if (!int.TryParse(partB, out var intB)) return false;
  if (intA < 0) intB *= -1;
  var dp = double.Parse("1".PadRight(partB.Length + 1, '0'));

  result = intA + intB / dp;
  return true;
}

Upvotes: 0

Codigo
Codigo

Reputation: 398

In Android Xamarin, I ran into the same issue several times. Some solutions worked until the Android got upgraded into a new version, then the problem came out again. So I came with an universal solution, which works fine. I read the numeric input as text, then parse it into decimal with a custom parser.

The custom parser is returning 0 when parsing into decimal is not possible. It does allow input text containing decimal number with either comma or dot, with no group separators:

public static decimal ParseTextToDecimal(string decimalText)
        {
            if (decimalText == String.Empty) return 0;
            string temp = decimalText.Replace(',', '.');
            var decText = temp.Split('.');
            if (!Int32.TryParse(decText[0], out int integerPart)) return 0;
            if (decText.Length == 1) return integerPart;
            if (decText.Length == 2)
            {
                if (!Int32.TryParse(decText[1], out int decimalPart)) return 0;

                decimal powerOfTen = 10m;
                for (int i = 1; i < decText[1].Length; i++) powerOfTen *= 10;
                return integerPart + decimalPart / powerOfTen;
            }
            return 0; // there were two or more decimal separators, which is a clear invalid input
        }

Upvotes: -1

John Willemse
John Willemse

Reputation: 6698

The solution I use is to simply show the user what the parsed value is.

I have a custom TextBox control which verifies the input when the control loses focus and such. If the control expects a floating point value (which is a property), then it will try to parse the value entered. If the TryParse succeeds, I display the out value in the control's text.

This way, when a user enters 12.3 the value might change to 123 because in the current culture 12,3 is expected. It's then up to them to decide to correct this.

Upvotes: 0

ace lafit
ace lafit

Reputation: 259

I know the thread is a little bit older, but I try to provide an answer.

I use regular expression to determine the used number format in the string. The regex also matches numbers without decimal separators ("12345").

var numberString = "1,234.56"; // en
// var numberString = "1.234,56"; // de
var cultureInfo = CultureInfo.InvariantCulture;
// if the first regex matches, the number string is in us culture
if (Regex.IsMatch(numberString, @"^(:?[\d,]+\.)*\d+$"))
{
    cultureInfo = new CultureInfo("en-US");
}
// if the second regex matches, the number string is in de culture
else if (Regex.IsMatch(numberString, @"^(:?[\d.]+,)*\d+$"))
{
    cultureInfo = new CultureInfo("de-DE");
}
NumberStyles styles = NumberStyles.Number;
bool isDouble = double.TryParse(numberString, styles, cultureInfo, out number);

HTH

Thomas

Upvotes: 20

ng80092b
ng80092b

Reputation: 667

I found a solution, I'm a beginner on this regional and comma-dots theme so if you have comments to improve the understanding of this please be welcome.

We start of by getting what decimal separator the user has set in his regional options outside before the Form{InitializeComponent();} (I want a universal variable that will allow me to correct the code)

 char sepdec = Convert.ToChar(CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator);

In the tryParse, to get it to behave universally we will read the dots and commas in the string, and turn them into the decimal separator we defined as sepdec 

decimal.TryParse(str.Replace(",",sepdec.ToString()).Replace(".",sepdec.ToString()),  out somevariable);

I hope this helps, please comment improvement suggestions!

Upvotes: 0

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