Fastest way to check if string contains only digits

Question

I know a few ways how to check this  regex int parse tryparse looping   can anyone tell me what is the fastest way to check   the need is to only CHECK no need to actually parse   this is not the same question as  How do I identify if a string is a number   the question is not only about how identify  but about what is the fastest method

User · Answer

Very Clever and easy way to detect your string is contains only digits or not is this way   string s    12fg    if s All char IsDigit        return true     contains only digits   else      return false     contains not only digits

User · Answer

if it is a single string   if  str All Char IsDigit          string contains only digits    if it is a list of strings   if  lstStr All s   gt  s All Char IsDigit           List of strings contains only digits

User · Answer

I like Linq and to make it exit on first mismatch you can do this   string str    0129834X33   bool isAllDigits    str Any  ch  gt  ch  lt   0     ch  gt   9

User · Answer

You can do this in a one line LINQ statement  OK  I realise this is not necessarily the fastest  so doesn t technically answer the question  but it s probably the easiest to write   str All c   gt  c  gt    0   amp  amp  c  lt    9

User · Answer

Probably the fastest way is   myString All c   gt  char IsDigit c     Note  it will return True in case your string is empty which is incorrect  if you not considering empty as valid number digit

User · Answer

This might be coming super late   but I m sure it will help someone  as it helped me           private static bool IsDigitsOnly string str                        return str All c   gt  c  gt    0   amp  amp  c  lt    9

User · Answer

Try this code   bool isDigitsOnly string str       try            int number   Convert ToInt32 str         return true          catch  Exception             return false

User · Answer

bool IsDigitsOnly string str        foreach  char c in str                if  c  lt   0     c  gt   9               return false             return true      Will probably be the fastest way to do it

User · Answer

What about char IsDigit myChar

User · Answer

Function with empty validation   public static bool IsDigitsOnly string str                           return  string IsNullOrEmpty str   amp  amp  str All char IsDigit

User · Answer

You could simply do this using LINQ  return str All char IsDigit      All returns true for empty strings and exception for null strings  char IsDigit is true for all Unicode characters

User · Answer

You can try using Regular Expressions by testing the input string to have only digits  0-9  by using the  IsMatch string input  string pattern  method in C    using System  using System Text RegularExpression   public namespace MyNS       public class MyClass               public void static Main string   args                         string input   Console ReadLine                 bool containsNumber   ContainsOnlyDigits input                      private bool ContainOnlyDigits  string input                        bool containsNumbers   true              if   Regex IsMatch input     d                                  containsNumbers   false                            return containsNumbers                      Regards

User · Answer

this will work perfectly  there is many other ways but this would work  bool IsDigitsOnly string str                if  str Length  gt  0   if contains characters                       foreach  char c in str   assign character to c                               if  c  lt   0     c  gt   9    check if its outside digit range                     return false                         else  empty string                       return false   empty string                     return true   only digits

User · Answer

Another approach  string str    quot 12345 quot   bool containsOnlyDigits   true  try   if Convert ToInt32 str   lt  0   containsOnlyDigits   false      catch   containsOnlyDigits   false     Here  if the statement Convert ToInt32 str  fails  then string does not contain digits only  Another possibility is that if the string has  quot -12345 quot  which gets converted to -12345 successfully  then there is a check for verifying that the number converted is not less than zero

User · Answer

public bool CheckforDigits string x            int tr        return x All r  gt  int TryParse r ToString    out tr

User · Answer

If you are concerned about performance  use neither int TryParse nor Regex - write your own  simple  function  DigitsOnly or  DigitsOnly2 below  but not DigitsOnly3 - LINQ seems to incur a significant overhead    Also  be aware that int TryParse will fail if the string is too long to  fit  into int   This simple benchmark     class Program        static bool DigitsOnly string s            int len   s Length          for  int i   0  i  lt  len    i                char c   s i               if  c  lt   0     c  gt   9                   return false                    return true             static bool DigitsOnly2 string s            foreach  char c in s                if  c  lt   0     c  gt   9                   return false                    return true             static bool DigitsOnly3 string s            return s All c   gt  c  gt    0   amp  amp  c  lt    9               static void Main string   args             const string s1    916734184           const string s2    916734a84            const int iterations   1000000          var sw   new Stopwatch             sw Restart            for  int i   0   i  lt  iterations    i                bool success   DigitsOnly s1               bool failure   DigitsOnly s2                     sw Stop            Console WriteLine string Format  DigitsOnly   0    sw Elapsed             sw Restart            for  int i   0  i  lt  iterations    i                bool success   DigitsOnly2 s1               bool failure   DigitsOnly2 s2                     sw Stop            Console WriteLine string Format  DigitsOnly2   0    sw Elapsed             sw Restart            for  int i   0  i  lt  iterations    i                bool success   DigitsOnly3 s1               bool failure   DigitsOnly3 s2                     sw Stop            Console WriteLine string Format  DigitsOnly3   0    sw Elapsed             sw Restart            for  int i   0  i  lt  iterations    i                int dummy              bool success   int TryParse s1  out dummy               bool failure   int TryParse s2  out dummy                     sw Stop            Console WriteLine string Format  int TryParse   0    sw Elapsed             sw Restart            var regex   new Regex    0-9      RegexOptions Compiled           for  int i   0  i  lt  iterations    i                bool success   regex IsMatch s1               bool failure   regex IsMatch s2                     sw Stop            Console WriteLine string Format  Regex IsMatch   0    sw Elapsed                   produces the following result     DigitsOnly  00 00 00 0346094 DigitsOnly2  00 00 00 0365220 DigitsOnly3  00 00 00 2669425 int TryParse  00 00 00 3405548 Regex IsMatch  00 00 00 7017648

User · Answer

The char already has an IsDigit char c  which does this    public static bool IsDigit char c              if   char IsLatin1 c           return CharUnicodeInfo GetUnicodeCategory c     UnicodeCategory DecimalDigitNumber        if   int  c  gt   48          return  int  c  lt   57        else         return false          You can simply do this   var theString    839278   bool digitsOnly   theString All char IsDigit

User · Answer

This should work   Regex IsMatch  124      0-9      RegexOptions Compiled    int Parse or int TryParse won t always work  because the string might contain more digits that an int can hold   If you are going to do this check more than once it is useful to use a compiled regex - it takes more time the first time  but is much faster after that

User · Answer

Here s some benchmarks based on 1000000 parses of the same string   Updated for release stats   IsDigitsOnly  384588 TryParse      639583 Regex         1329571   Here s the code  looks like IsDigitsOnly is faster   class Program       private static Regex regex   new Regex    0-9      RegexOptions Compiled        static void Main string   args                Stopwatch watch   new Stopwatch            string test   int MaxValue ToString            int value           watch Start            for int i 0  i lt  1000000  i                          int TryParse test  out value                     watch Stop            Console WriteLine  TryParse    watch ElapsedTicks            watch Reset            watch Start            for  int i   0  i  lt  1000000  i                          IsDigitsOnly test                     watch Stop            Console WriteLine  IsDigitsOnly      watch ElapsedTicks            watch Reset            watch Start            for  int i   0  i  lt  1000000  i                          regex IsMatch test                     watch Stop            Console WriteLine  Regex      watch ElapsedTicks            Console ReadLine               static bool IsDigitsOnly string str                foreach  char c in str                        if  c  lt   0     c  gt   9                   return false                     return true            Of course it s worth noting that TryParse does allow leading trailing whitespace as well as culture specific symbols  It s also limited on length of string

User · Answer

Can be about 20  faster by using just one comparison per char and for instead of foreach   bool isDigits string s          if  s    null    s        return false        for  int i   0  i  lt  s Length  i             if   s i     0    gt  9               return false        return true         Code used for testing  always profile because the results depend on hardware  versions  order  etc     static bool isDigitsFr string s    if  s    null    s        return false  for  int i   0  i  lt  s Length  i    if  s i   lt   0     s i   gt   9   return false  return true    static bool isDigitsFu string s    if  s    null    s        return false  for  int i   0  i  lt  s Length  i    if   uint  s i  -  0    gt  9  return false  return true    static bool isDigitsFx string s    if  s    null    s        return false  for  int i   0  i  lt  s Length  i    if   s i     0    gt  9  return false  return true    static bool isDigitsEr string s    if  s    null    s        return false  foreach  char c in s  if  c  lt   0     c  gt   9   return false  return true    static bool isDigitsEu string s    if  s    null    s        return false  foreach  char c in s  if   uint  c -  0    gt  9  return false  return true    static bool isDigitsEx string s    if  s    null    s        return false  foreach  char c in s  if   c    0    gt  9  return false  return true    static void test         var w   new Stopwatch    bool b  var s   int MaxValue       int r   12345678 2  var ss   new SortedSet lt string gt       s   string Concat Enumerable Range 0  127  Select i   gt    char i    0    lt  10   1   0        w Restart    for  int i   0  i  lt  r  i    b   s All char IsDigit   w Stop    ss Add w Elapsed     All  IsDigit         w Restart    for  int i   0  i  lt  r  i    b   s All c   gt  c  gt    0   amp  amp  c  lt    9    w Stop    ss Add w Elapsed     All  lt  gt          w Restart    for  int i   0  i  lt  r  i    b   s All c   gt   c    0    lt  10   w Stop    ss Add w Elapsed      All           w Restart    for  int i   0  i  lt  r  i    b   isDigitsFr s   w Stop    ss Add w Elapsed     for      lt  gt         w Restart    for  int i   0  i  lt  r  i    b   isDigitsFu s   w Stop    ss Add w Elapsed     for     -        w Restart    for  int i   0  i  lt  r  i    b   isDigitsFx s   w Stop    ss Add w Elapsed     for              w Restart    for  int i   0  i  lt  r  i    b   isDigitsEr s   w Stop    ss Add w Elapsed     foreach  lt  gt         w Restart    for  int i   0  i  lt  r  i    b   isDigitsEu s   w Stop    ss Add w Elapsed     foreach -        w Restart    for  int i   0  i  lt  r  i    b   isDigitsEx s   w Stop    ss Add w Elapsed     foreach          MessageBox Show string Join   n   ss    return      Results on Intel i5-3470   3 2GHz  VS 2015  NET 4 6 1 Release mode and optimizations enabled   time    method          ratio 0 7776  for             1 0000  0 7984  foreach -       1 0268  0 8066  foreach         1 0372  0 8940  for     -       1 1497  0 8976  for      lt  gt       1 1543  0 9456  foreach  lt  gt       1 2160  4 4559   All  lt  gt          5 7303  4 7791   All            6 1458  4 8539   All  IsDigit   6 2421      For anyone tempted to use the shorter methods  note that     All results in true for empty strings and exception for null strings char IsDigit is true for all Unicode characters in the Nd category int TryParse also allows white spase and sign characters

[c#] Fastest way to check if string contains only digits

Examples related to c#