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

Question

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

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var doublePattern        lt integer gt  0-9               lt fraction gt  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

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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    quot   0-9   -   quot    quot  quot     Then we split up the number into the whole number and decimal number  string   decimalParsed   Regex Split stringAmount    quot             d 2    quot      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  quot   quot    quot  quot   Replace  quot   quot    quot  quot     if  wholeAmount IsNullOrEmpty            wholeAmount    quot 0 quot    Now we handle the decimal part  if any  string decimalAmount    quot 00 quot    if  decimalParsed Length    2                decimalAmount   decimalParsed 1          Finally we can put the whole and decimal together and parse the Double  double amount     quot  wholeAmount   decimalAmount  quot  ToDouble     This will handle 200 00  1 000 00   1 000   1 000 33   2 000 000 78 etc

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Double Parse  3 5  Replace            CultureInfo InvariantCulture    Replace the comma with a point before parsing  Useful in countries with a comma as decimal separator  Think about limiting user input  if necessary  to one comma or point

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I improved the code of  JanW as well     I need it to format results from medical instruments  and they also send   1000    23 3e02    350E-02   and  NEGATIVE    private string FormatResult string vResult      string output    string input   vResult        Unify string  no spaces  only      output   input Trim   Replace          Replace                  Split it on points   string   split   output Split          if  split Count    gt  1             Take all parts except last     output   string Join     split Take split Count   - 1  ToArray             Combine token parts with last part     output   string Format   0   1    output  split Last           string sfirst   output Substring 0  1      try         if  sfirst      lt      sfirst      gt                output   output Replace sfirst             double res   Double Parse output         return String Format   1  0 0         res  sfirst             else             double res   Double Parse output         return String Format   0 0         res               catch         return output

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I think it is the best answer   public static double StringToDouble string toDouble        toDouble   toDouble Replace              Replace every comma with dot        Count dots in toDouble  and if there is more than one dot  throw an exception        Value such as  123 123 123  can t be converted to double     int dotCount   0      foreach  char c in toDouble  if  c         dotCount      Increments dotCount for each dot in toDouble     if  dotCount  gt  1  throw new Exception      If in toDouble is more than one dot  it means that toCount is not a double      string left   toDouble Split      0     Everything before the dot     string right   toDouble Split      1     Everything after the dot      int iLeft   int Parse left     Convert strings to ints     int iRight   int Parse right          We must use Math Pow   instead of       double d   iLeft    iRight   Math Pow 10  - right Length         return d

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double Parse  3 5   CultureInfo InvariantCulture

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I usualy use a multi-culture function to parse user input  mostly because if someone is used to the numpad and is using a culture that use a comma as the decimal separator  that person will use the point of the numpad instead of a comma   public static double GetDouble string value  double defaultValue        double result         Try parsing in the current culture     if   double TryParse value  System Globalization NumberStyles Any  CultureInfo CurrentCulture  out result   amp  amp            Then try in US english          double TryParse value  System Globalization NumberStyles Any  CultureInfo GetCultureInfo  en-US    out result   amp  amp            Then in neutral language          double TryParse value  System Globalization NumberStyles Any  CultureInfo InvariantCulture  out result                 result   defaultValue             return result      Beware though   nikie comments are true  To my defense  I use this function in a controlled environment where I know that the culture can either be en-US  en-CA or fr-CA  I use this function because in French  we use the comma as a decimal separator  but anybody who ever worked in finance will always use the decimal separator on the numpad  but this is a point  not a comma  So even in the fr-CA culture  I need to parse number that will have a point as the decimal separator

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I think 100  correct conversion isn t possible  if the value comes from a user input  e g  if the value is 123 456  it can be a grouping or it can be a decimal point  If you really need 100  you have to describe your format and throw an exception if it is not correct   But I improved the code of JanW  so we get a little bit more ahead to the 100   The idea behind is  that if the last separator is a groupSeperator  this would be more an integer type  than a double   The added code is in the first if of GetDouble   void Main         List lt string gt  inputs   new List lt string gt               1 234 567 89            1 234 567 89            1 234 567 89            1 234 567 89            1234567 89            1234567 89            123456789            123 456 789            123 456 789               foreach string input in inputs            Console WriteLine GetDouble input 0d              public static double GetDouble string value  double defaultValue        double result      string output          Check if last seperator  groupSeperator     string groupSep   System Globalization CultureInfo CurrentCulture NumberFormat NumberGroupSeparator      if  value LastIndexOf groupSep    4    value Count                  bool tryParse   double TryParse value  System Globalization NumberStyles Any  System Globalization CultureInfo CurrentCulture  out result           result   tryParse   result   defaultValue            else                  Unify string  no spaces  only             output   value Trim   Replace      string Empty  Replace                        Split it on points         string   split   output Split                if  split Count    gt  1                           Take all parts except last             output   string Join string Empty  split Take split Count  -1  ToArray                     Combine token parts with last part             output   string Format   0   1    output  split Last                          Parse double invariant         result   double Parse output  System Globalization CultureInfo InvariantCulture             return result

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I couldn t write a comment  so I write here   double Parse  3 5   CultureInfo InvariantCulture  is not a good idea  because in Canada we write 3 5 instead of 3 5 and this function gives us 35 as a result   I tested both on my computer   double Parse  3 5   CultureInfo InvariantCulture  -- gt  3 5 OK double Parse  3 5   CultureInfo InvariantCulture  -- gt  35 not OK   This is a correct way that Pierre-Alain Vigeant mentioned  public static double GetDouble string value  double defaultValue        double result          Try parsing in the current culture     if   double TryParse value  System Globalization NumberStyles Any  CultureInfo CurrentCulture  out result   amp  amp             Then try in US english          double TryParse value  System Globalization NumberStyles Any  CultureInfo GetCultureInfo  en-US    out result   amp  amp             Then in neutral language          double TryParse value  System Globalization NumberStyles Any  CultureInfo InvariantCulture  out result                 result   defaultValue            return result

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System Globalization CultureInfo ci   System Globalization CultureInfo CurrentCulture   string  pos   dblstr Replace          ci NumberFormat NumberDecimalSeparator  Replace              ci NumberFormat NumberDecimalSeparator    double  dbl   double Parse  pos

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string testString1    2 457   string testString2    2 457       double testNum   0 5  char decimalSepparator  decimalSepparator   testNum ToString   1    Console WriteLine double Parse testString1 Replace      decimalSepparator  Replace      decimalSepparator     Console WriteLine double Parse testString2 Replace      decimalSepparator  Replace      decimalSepparator

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It s difficult without specifying what decimal separator to look for  but if you do  this is what I m using       public static double Parse string str  char decimalSep                string s   GetInvariantParseString str  decimalSep           return double Parse s  System Globalization CultureInfo InvariantCulture              public static bool TryParse string str  char decimalSep  out double result                   NumberStyles Float   NumberStyles AllowThousands got from Reflector         return double TryParse GetInvariantParseString str  decimalSep   NumberStyles Float   NumberStyles AllowThousands  System Globalization CultureInfo InvariantCulture  out result              private static string GetInvariantParseString string str  char decimalSep                str   str Replace                    if  decimalSep                     str   SwapChar str  decimalSep                 return str            public static string SwapChar string value  char from  char to                if  value    null              throw new ArgumentNullException  value             StringBuilder builder   new StringBuilder             foreach  var item in value                        char c   item              if  c    from                  c   to              else if  c    to                  c   from               builder Append c                     return builder ToString               private static void ParseTestErr string p  char p 2                double res          bool b   TryParse p  p 2  out res           if  b              throw new Exception               private static void ParseTest double p  string p 2  char p 3                double d   Parse p 2  p 3           if  d    p              throw new Exception               static void Main string   args                ParseTest 100100100 100   100 100 100 100                 ParseTest 100100100 100   100 100 100 100                 ParseTest 100100100100   100 100 100 100                 ParseTest 100100100100   100 100 100 100                 ParseTestErr  100 100 100 100                 ParseTestErr  100 100 100 100                 ParseTest 100100100100   100 100 100 100 0                 ParseTest 100100100 100   100 100 100 100                 ParseTest 100100100 100   100 100 100 100                 ParseTest 100100100100   100 100 100 100                 ParseTest 1234567 89   1 234 567 89                     ParseTest 1234567 89   1 234 567 89                     ParseTest 1234567 89   1 234 567 89                     ParseTest 1234567 89   1 234 567 89                    ParseTest 1234567 89   1234567 89                     ParseTest 1234567 89   1234567 89                  ParseTest 123456789   123456789                 ParseTest 123456789   123456789                 ParseTest 123456789   123 456 789                 ParseTest 1234567890   1 234 567 890                 This should work with any culture  It correctly fails to parse strings that has more than one decimal separator  unlike implementations that replace instead of swap

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Look  every answer above that proposes writing a string replacement by a constant string can only be wrong  Why  Because you don t respect the region settings of Windows  Windows assures the user to have the freedom to set whatever separator character s he wants  S He can open up the control panel  go into the region panel  click on advanced and change the character at any time  Even during your program run  Think of this  A good solution must be aware of this   So  first you will have to ask yourself  where this number is coming from  that you want to parse  If it s coming from input in the  NET Framework no problem  because it will be in the same format  But maybe it was coming from outside  maybe from a external server  maybe from an old DB that only supports string properties  There  the db admin should have given a rule in which format the numbers are to be stored  If you know for example that it will be an US DB with US format you can use this piece of code   CultureInfo usCulture   new CultureInfo  en-US    NumberFormatInfo dbNumberFormat   usCulture NumberFormat  decimal number   decimal Parse db numberString  dbNumberFormat     This will work fine anywhere on the world  And please don t use  Convert ToXxxx   The  Convert  class is thought only as a base for conversions in any direction  Besides  You may use the similar mechanism for DateTimes too

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The trick is to use invariant culture  to parse dot in all cultures   double Parse  3 5   System Globalization NumberStyles AllowDecimalPoint  System Globalization NumberFormatInfo InvariantInfo

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Instead of having to specify a locale in all parses  I prefer to set an application wide locale  although if string formats are not consistent across the app  this might not work   CultureInfo DefaultThreadCurrentCulture   new CultureInfo  pt-PT    CultureInfo DefaultThreadCurrentUICulture   new CultureInfo  pt-PT      Defining this at the begining of your application will make all double parses expect a comma as the decimal delimiter  You can set an appropriate locale so that the decimal and thousands separator fits the strings you are parsing

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Multiply the number and then divide it by what you multiplied it by before   For example   perc   double Parse  3 555  1000  result   perc 1000

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The below is less efficient  but I use this logic  This is valid only if you have two digits after decimal point   double val   if  temp Text Split      Length  gt  1        val   double Parse temp Text Split      0         if  temp Text Split      1  Length    1          val     0 1   double Parse temp Text Split      1         else         val     0 01   double Parse temp Text Split      1       else     val   double Parse RR temp Text

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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 lt char gt  doubleAsCharList   doubleAsString ToList         if  doubleAsCharList Where ch   gt  ch           ch         Count    lt   1                double TryParse doubleAsString Replace                        System Globalization NumberStyles Any              CultureInfo InvariantCulture              out result             else               if  doubleAsCharList Where ch   gt  ch         Count    lt   1              amp  amp  doubleAsCharList Where ch   gt  ch         Count    gt  1                        double TryParse doubleAsString Replace      string Empty                   System Globalization NumberStyles Any                  CultureInfo InvariantCulture                  out result                     else if  doubleAsCharList Where ch   gt  ch         Count    lt   1              amp  amp  doubleAsCharList Where ch   gt  ch         Count    gt  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

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The following code does the job in any scenario  It s a little bit parsing   List lt string gt  inputs   new List lt string gt           1 234 567 89        1 234 567 89        1 234 567 89        1 234 567 89        123456789        1234567 89        1234567 89      string output   foreach  string input in inputs           Unify string  no spaces  only        output   input Trim   Replace          Replace                    Split it on points     string   split   output Split            if  split Count    gt  1                   Take all parts except last         output   string Join     split Take split Count  -1  ToArray                 Combine token parts with last part         output   string Format   0   1    output  split Last                   Parse double invariant     double d   double Parse output  CultureInfo InvariantCulture       Console WriteLine d

[c#] How do I parse a string with a decimal point to a double?

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