Regular expression for decimal number

Question

I need to validate a textbox input and can only allow decimal inputs like  X XXX  only one digit before decimal sign and a precision of 3    I m using C  and try this   0-9      0-9  1 2

User · Answer

d 1     d 1 3     Match a single digit 0  9    d 1       Exactly 1 times    1    Match the regular expression below and capture its match into backreference number 1       d 1 3         Between zero and one times  as many times as possible  giving back as needed  greedy           Match the character         literally           Match a single digit 0  9    d 1 3          Between one and 3 times  as many times as possible  giving back as needed  greedy     1 3      Created with RegexBuddy   Matches  1 1 2 1 23 1 234

User · Answer

I just found TryParse   has an issue that it accounts for thousands seperator   Example in En-US  10 36 00 is ok   I had a specific scenario where the thousands seperator should not be considered and hence regex  d    d  turned out to be the best bet  Of course had to keep the decimal char variable for different locales

User · Answer

As I tussled with this  TryParse in 3 5 does have NumberStyles   The following code should also do the trick without Regex to ignore thousands seperator   double TryParse length  NumberStyles AllowDecimalPoint CultureInfo CurrentUICulture  out lengthD     Not relevant to the original question asked but confirming that TryParse   indeed is a good option

User · Answer

In general  i e  unlimited decimal places    -    1-9  d   0   0  1-9  0  1-9

User · Answer

In  NET  I recommend to dynamically build the regular expression with the decimal separator of the current cultural context   using System Globalization        NumberFormatInfo nfi   NumberFormatInfo CurrentInfo  Regex re   new Regex       d                          Regex Escape nfi CurrencyDecimalSeparator                           d 1 2          You might want to pimp the regexp by allowing 1000er separators the same way as the decimal separator

User · Answer

There is an alternative approach  which does not have I18n problems  allowing     or     but not both   Decimal TryParse   Just try converting  ignoring the value   bool IsDecimalFormat string input      Decimal dummy    return Decimal TryParse input  out dummy       This is significantly faster than using a regular expression  see below    The overload of Decimal TryParse can be used for finer control      Performance test results  Decimal TryParse  0 10277ms  Regex  0 49143ms  Code  PerformanceHelper Run is a helper than runs the delegate for passed iteration count and returns the average TimeSpan     using System  using System Text RegularExpressions  using DotNetUtils Diagnostics   class Program       static private readonly string   TestData   new string              10 0            10 0            0 1             1            Snafu           new string  x   10000           new string  2   10000           new string  0   10000              static void Main string   args            Action parser        gt                int n   TestData Length              int count   0              for  int i   0  i  lt  n    i                    decimal dummy                  count    Decimal TryParse TestData i   out dummy    1   0                                   Regex decimalRegex   new Regex     0-9         0-9  1 3                Action regex        gt                int n   TestData Length              int count   0              for  int i   0  i  lt  n    i                    count    decimalRegex IsMatch TestData i     1   0                                    var paserTotal   0 0          var regexTotal   0 0          var runCount   10          for  int run   1  run  lt   runCount    run                var parserTime   PerformanceHelper Run 10000  parser               var regexTime   PerformanceHelper Run 10000  regex                Console WriteLine  Run   2   Decimal TryParse   0 ms  Regex   1 ms                                 parserTime TotalMilliseconds                                 regexTime TotalMilliseconds                                run               paserTotal    parserTime TotalMilliseconds              regexTotal    regexTime TotalMilliseconds                     Console WriteLine  Overall averages  Decimal TryParse   0 ms  Regex   1 ms                             paserTotal runCount                            regexTotal runCount

User · Answer

0-9       0-9  1 3       It allows   0 1 1 2 1 02 1 003 1 030 1 2 1 23 1 234   BUT NOT    1  1 12 1 12 1 1  1  1 2345 1 2345

[c#] Regular expression for decimal number

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