[c#] Parse strings to double with comma and point

I am trying to write a function which basically converts an array of strings to an array of strings where all the doubles in the array are rounded to the number of decimalplaces i set. There can also be strings in the array which are no double values at all.

string[,] values = new string[1, 3];

values[0, 0] = "hello";
values[0, 1] = "0.123";
values[0, 2] = "0,123";

int decimalPlaces = 2;

double tmp;
string format = "F" + decimalPlaces.ToString();
IFormatProvider provider = CultureInfo.InvariantCulture;
for (int i = 0; i < values.GetLength(0); i++)
{
    for (int j = 0; j < values.GetLength(1); j++)
    {
        if (double.TryParse(values[i, j], out tmp))
        {
            values[i, j] = tmp.ToString(format, provider);
        }
    }
}

Console.ReadLine();

The result has to be: "hello" , "0.12", "0.12" but it is "hello", "123.00", "0.12" will treat the comma in the wrong way. Does anyone have a simple and efficient solution for this?

Make two static cultures, one for comma and one for point.

    var commaCulture = new CultureInfo("en")
    {
        NumberFormat =
        {
            NumberDecimalSeparator = ","
        }
    };

    var pointCulture = new CultureInfo("en")
    {
        NumberFormat =
        {
            NumberDecimalSeparator = "."
        }
    };

Then use each one respectively, depending on the input (using a function):

    public double ConvertToDouble(string input)
    {
        input = input.Trim();

        if (input == "0") {
            return 0;
        }

        if (input.Contains(",") && input.Split(',').Length == 2)
        {
            return Convert.ToDouble(input, commaCulture);
        }

        if (input.Contains(".") && input.Split('.').Length == 2)
        {
            return Convert.ToDouble(input, pointCulture);
        }

        throw new Exception("Invalid input!");
    }

Then loop through your arrays

    var strings = new List<string> {"0,12", "0.122", "1,23", "00,0", "0.00", "12.5000", "0.002", "0,001"};
    var doubles = new List<double>();

    foreach (var value in strings) {
        doubles.Add(ConvertToDouble(value));
    }

This should work even though the host environment and culture changes.

You can check if the string contains a decimal point using

string s="";

        if (s.Contains(','))
        { 
        //treat as double how you wish
        }

and then treat that as a decimal, otherwise just pass the non-double value along.

The problem is that you (or the system) cannot distinguish a decimal separator from a thousands separator when they can be both a comma or dot. For example:

In my culture,

1.123 is a normal notation for a number above 1000; whereas

1,123 is a number near 1.

Using the invariant culture defaults to using the dot as a decimal separator. In general you should ensure that all numbers are written using the same constant culture on all systems (e.g. the invariant culture).

If you are sure that your numbers never contain anything other than a comma or dot for a decimal separator (i.e. no thousands separators), I'd String.Replace() the comma with a dot and do the rest as you did.

Otherwise, you'll have a hard time programming something that can distinguish 1.123 from 1,123 without knowing the culture.

To treat both , and . as decimal point you must not only replace one with the other, but also make sure the Culture used parsing interprets it as a decimal point.

text = text.Replace(',', '.');
return double.TryParse(text, NumberStyles.Any, CultureInfo.InvariantCulture, out value);

try this... it works for me.

double vdouble = 0;
string sparam = "2,1";

if ( !Double.TryParse( sparam, NumberStyles.Float, CultureInfo.InvariantCulture, out vdouble ) )
{
    if ( sparam.IndexOf( '.' ) != -1 )
    {
        sparam = sparam.Replace( '.', ',' );
    }
    else
    {
        sparam = sparam.Replace( ',', '.' );
    }

    if ( !Double.TryParse( sparam, NumberStyles.Float, CultureInfo.InvariantCulture, out vdouble ) )
    {
        vdouble = 0;
    }
}

Use this overload of double.TryParse to specify allowed formats:

Double.TryParse Method (String, NumberStyles, IFormatProvider, Double%)

By default, double.TryParse will parse based on current culture specific formats.

You DO NOT NEED to replace the comma and dot..

I have had the very same problem. The reason is simple, the conversion culture plays a big role in which the comma or a dot is interpreted. I use a German culture where the comma distinguish the fractions, where as elsewhere the dot does the job.

Here I made a complete example to make the difference clear.

string[] doubleStrings = {"hello", "0.123", "0,123"};
double localCultreResult;
foreach (var doubleString in doubleStrings)
{
    double.TryParse(doubleString, NumberStyles.Any, CultureInfo.CurrentCulture, out localCultreResult);
    Console.WriteLine(string.Format("Local culture results for the parsing of {0} is {1}", doubleString, localCultreResult));
}

double invariantCultureResult;
foreach (var doubleString in doubleStrings)
{
    double.TryParse(doubleString, NumberStyles.Any, CultureInfo.InvariantCulture, out invariantCultureResult);
    Console.WriteLine(string.Format("Invariant culture results for the parsing of {0} is {1}", doubleString, invariantCultureResult));
}

The results is the following:

Play around with the culture and you will get the result you need.

Extension to parse decimal number from string.

• No matter number will be on the beginning, in the end, or in the middle of a string.
• No matter if there will be only number or lot of "garbage" letters.
• No matter what is delimiter configured in the cultural settings on the PC: it will parse dot and comma both correctly.

• Ability to set decimal symbol manually.

  public static class StringExtension
  {
      public static double DoubleParseAdvanced(this string strToParse, char decimalSymbol = ',')
      {
          string tmp = Regex.Match(strToParse, @"([-]?[0-9]+)([\s])?([0-9]+)?[." + decimalSymbol + "]?([0-9 ]+)?([0-9]+)?").Value;
  
          if (tmp.Length > 0 && strToParse.Contains(tmp))
          {
              var currDecSeparator = System.Windows.Forms.Application.CurrentCulture.NumberFormat.NumberDecimalSeparator;
  
              tmp = tmp.Replace(".", currDecSeparator).Replace(decimalSymbol.ToString(), currDecSeparator);
  
              return double.Parse(tmp);
          }
  
          return 0;
      }
  }
  

How to use:

"It's 4.45 O'clock now".DoubleParseAdvanced(); // will return 4.45
"It's 4,45 O'clock now".DoubleParseAdvanced(); // will return 4.45
"It's 4:45 O'clock now".DoubleParseAdvanced(':'); // will return 4.45