How do I replace multiple spaces with a single space in C

Question

How can I replace multiple spaces in a string with only one space in C    Example   1 2 3  4    5   would be   1 2 3 4 5

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Mix of StringBuilder and Enumerable Aggregate   as extension method for strings   using System  using System Linq  using System Text   public static class StringExtension       public static string StripSpaces this string s                return s Aggregate new StringBuilder     acc  c    gt                        if  c           acc Length  gt  0  amp  amp  acc acc Length-1                          acc Append c                return acc             ToString               public static void Main                 Console WriteLine        StringExtension StripSpaces  1   Hello       World  2                         Input    1   Hello       World  2       Output    1 Hello World 2

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You can simply do this in one line solution   string s    welcome to  london   s Replace            Replace           Replace               You can choose other brackets  or even other characters  if you like

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I like to use   myString   Regex Replace myString     s            Since it will catch runs of any kind of whitespace  e g  tabs  newlines  etc   and replace them with a single space

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I can remove whitespaces with this   while word contains          double space    word   word Replace              replace double space by single space  word   word trim      to remove single whitespces from start  amp  end

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I think Matt s answer is the best  but I don t believe it s quite right   If you want to replace newlines  you must use   myString   Regex Replace myString     s         RegexOptions Multiline

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Consolodating other answers  per Joel  and hopefully improving slightly as I go   You can do this with Regex Replace     string s   Regex Replace           1  2    4 5              2                       Or with String Split     static class StringExtensions       public static string Join this IList lt string gt  value  string separator                return string Join separator  value ToArray                     string s         1  2    4 5  Split           ToCharArray         StringSplitOptions RemoveEmptyEntries       Join

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string sentence    This is a sentence with multiple    spaces   RegexOptions options   RegexOptions None  Regex regex   new Regex      2     options        sentence   regex Replace sentence

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Regex can be rather slow even with simple tasks   This creates an extension method that can be used off of any string               public static class StringExtension               public static String ReduceWhitespace this String value                        var newString   new StringBuilder                bool previousIsWhitespace   false              for  int i   0  i  lt  value Length  i                                  if  Char IsWhiteSpace value i                                          if  previousIsWhitespace                                                continue                                             previousIsWhitespace   true                                    else                                       previousIsWhitespace   false                                     newString Append value i                               return newString ToString                      It would be used as such   string testValue    This contains     too          much  whitespace   testValue   testValue ReduceWhitespace       testValue    This contains too much whitespace

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Many answers are providing the right output but for those looking for the best performances  I did improve Nolanar s answer  which was the best answer for performance  by about 10    public static string MergeSpaces this string str         if  str    null                return null            else               StringBuilder stringBuilder   new StringBuilder str Length            int i   0          foreach  char c in str                        if  c           i    0    str i - 1                          stringBuilder Append c               i                      return stringBuilder ToString

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try this method    private string removeNestedWhitespaces char   st        StringBuilder sb   new StringBuilder        int indx   0  length   st Length      while  indx  lt  length                sb Append st indx            indx            while  indx  lt  length  amp  amp  st indx                      indx            if sb Length  gt  1   amp  amp  sb 0                      sb Append                 return sb ToString        use it like this     string test   removeNestedWhitespaces  1 2 3  4    5  toCharArray

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no Regex  no Linq    removes leading and trailing spaces as well as reducing any embedded multiple space segments to one space  string myString       0 1 2  3   4               5     myString   string Join      myString Split new char             StringSplitOptions RemoveEmptyEntries      result  0 1 2 3 4 5

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I can remove whitespaces with this   while word contains          double space    word   word Replace              replace double space by single space  word   word trim      to remove single whitespces from start  amp  end

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string xyz    1   2   3   4   5   xyz   string Join       xyz Split  new char            StringSplitOptions RemoveEmptyEntries

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myString   Regex Replace myString     2

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I just wrote a new Join that I like  so I thought I d re-answer  with it   public static string Join lt T gt  this IEnumerable lt T gt  source  string separator        return string Join separator  source Select e   gt  e ToString    ToArray         One of the cool things about this is that it work with collections that aren t strings  by calling ToString   on the elements   Usage is still the same          string s         1  2    4 5  Split           ToCharArray         StringSplitOptions RemoveEmptyEntries       Join

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I looked over proposed solutions  could not find the one that would handle mix of white space characters acceptable for my case  for example   Regex Replace input    quot  s  quot    quot   quot   - it will eat your line breaks  if they are mixed with spaces  for example  n  n sequence will be replaced with   Regex Replace source    quot   s  s  quot    quot  1 quot   - it will depend on whitespace first character  meaning that it again might eat your line breaks Regex Replace source    quot     2   quot    quot   quot   - it won t work correctly when there s mix of whitespace characters - for example  quot  t  t  quot   Probably not perfect  but quick solution for me was  Regex Replace input    quot  s  quot     match    gt  match Value IndexOf   n    gt  -1    quot  n quot     quot   quot   RegexOptions Multiline   Idea is - line break wins over the spaces and tabs  This won t handle windows line breaks correctly  but it would be easy to adjust to work with that too  don t know regex that well - may be it is possible to fit into single pattern

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Without using regular expressions   while  myString IndexOf       StringComparison CurrentCulture     -1        myString   myString Replace                 OK to use on short strings  but will perform badly on long strings with lots of spaces

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For those  who don t like Regex  here is a method that uses the StringBuilder       public static string FilterWhiteSpaces string input                if  input    null              return string Empty           StringBuilder stringBuilder   new StringBuilder input Length           for  int i   0  i  lt  input Length  i                          char c   input i               if  i    0    c            c         amp  amp  input i - 1                           stringBuilder Append c                     return stringBuilder ToString            In my tests  this method was 16 times faster on average with a very large set of small-to-medium sized strings  compared to a static compiled Regex  Compared to a non-compiled or non-static Regex  this should be even faster   Keep in mind  that it does not remove leading or trailing spaces  only multiple occurrences of such

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I think Matt s answer is the best  but I don t believe it s quite right   If you want to replace newlines  you must use   myString   Regex Replace myString     s         RegexOptions Multiline

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Mysample string string str   quot hi you           are          a demo quot      Split the words based on white sapce var demo  str  Split      Where s   gt   string IsNullOrWhiteSpace s               Join the values back and add a single space in between str   string Join  quot   quot   demo      output  string str   quot hi you are a demo quot

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I just wrote a new Join that I like  so I thought I d re-answer  with it   public static string Join lt T gt  this IEnumerable lt T gt  source  string separator        return string Join separator  source Select e   gt  e ToString    ToArray         One of the cool things about this is that it work with collections that aren t strings  by calling ToString   on the elements   Usage is still the same          string s         1  2    4 5  Split           ToCharArray         StringSplitOptions RemoveEmptyEntries       Join

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Mix of StringBuilder and Enumerable Aggregate   as extension method for strings   using System  using System Linq  using System Text   public static class StringExtension       public static string StripSpaces this string s                return s Aggregate new StringBuilder     acc  c    gt                        if  c           acc Length  gt  0  amp  amp  acc acc Length-1                          acc Append c                return acc             ToString               public static void Main                 Console WriteLine        StringExtension StripSpaces  1   Hello       World  2                         Input    1   Hello       World  2       Output    1 Hello World 2

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myString   Regex Replace myString     2

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Consolodating other answers  per Joel  and hopefully improving slightly as I go   You can do this with Regex Replace     string s   Regex Replace           1  2    4 5              2                       Or with String Split     static class StringExtensions       public static string Join this IList lt string gt  value  string separator                return string Join separator  value ToArray                     string s         1  2    4 5  Split           ToCharArray         StringSplitOptions RemoveEmptyEntries       Join

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Another approach which uses LINQ    var list   str Split      Where s   gt   string IsNullOrWhiteSpace s     str   string Join      list

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This is a shorter version  which should only be used if you are only doing this once  as it creates a new instance of the Regex class every time it is called   temp   new Regex    2     Replace temp           If you are not too acquainted with regular expressions  here s a short explanation   The  2   makes the regex search for the character preceding it  and finds substrings between 2 and unlimited times  The  Replace temp       replaces all matches in the string temp with a space   If you want to use this multiple times  here is a better option  as it creates the regex IL at compile time   Regex singleSpacify   new Regex    2     RegexOptions Compiled   temp   singleSpacify Replace temp

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myString   Regex Replace myString     2

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I looked over proposed solutions  could not find the one that would handle mix of white space characters acceptable for my case  for example   Regex Replace input    quot  s  quot    quot   quot   - it will eat your line breaks  if they are mixed with spaces  for example  n  n sequence will be replaced with   Regex Replace source    quot   s  s  quot    quot  1 quot   - it will depend on whitespace first character  meaning that it again might eat your line breaks Regex Replace source    quot     2   quot    quot   quot   - it won t work correctly when there s mix of whitespace characters - for example  quot  t  t  quot   Probably not perfect  but quick solution for me was  Regex Replace input    quot  s  quot     match    gt  match Value IndexOf   n    gt  -1    quot  n quot     quot   quot   RegexOptions Multiline   Idea is - line break wins over the spaces and tabs  This won t handle windows line breaks correctly  but it would be easy to adjust to work with that too  don t know regex that well - may be it is possible to fit into single pattern

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It s much simpler than all that   while str Contains        str   str Replace

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try this method    private string removeNestedWhitespaces char   st        StringBuilder sb   new StringBuilder        int indx   0  length   st Length      while  indx  lt  length                sb Append st indx            indx            while  indx  lt  length  amp  amp  st indx                      indx            if sb Length  gt  1   amp  amp  sb 0                      sb Append                 return sb ToString        use it like this     string test   removeNestedWhitespaces  1 2 3  4    5  toCharArray

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Use the regex pattern                only space     var text   Regex Replace inputString

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It s much simpler than all that   while str Contains        str   str Replace

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I know this is pretty old  but ran across this while trying to accomplish almost the same thing  Found this solution in RegEx Buddy  This pattern will replace all double spaces with single spaces and also trim leading and trailing spaces   pattern    m             2    replacement   1   Its a little difficult to read since we re dealing with empty space  so here it is again with the  spaces  replaced with a        pattern    m             2      lt -- don t use this  just for illustration    The    m   construct enables the  multi-line  option  I generally like to include whatever options I can within the pattern itself so it is more self contained

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It s much simpler than all that   while str Contains        str   str Replace

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Without using regular expressions   while  myString IndexOf       StringComparison CurrentCulture     -1        myString   myString Replace                 OK to use on short strings  but will perform badly on long strings with lots of spaces

User · Answer

You can simply do this in one line solution   string s    welcome to  london   s Replace            Replace           Replace               You can choose other brackets  or even other characters  if you like

User · Answer

It s much simpler than all that   while str Contains        str   str Replace

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string xyz    1   2   3   4   5   xyz   string Join       xyz Split  new char            StringSplitOptions RemoveEmptyEntries

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I just wrote a new Join that I like  so I thought I d re-answer  with it   public static string Join lt T gt  this IEnumerable lt T gt  source  string separator        return string Join separator  source Select e   gt  e ToString    ToArray         One of the cool things about this is that it work with collections that aren t strings  by calling ToString   on the elements   Usage is still the same          string s         1  2    4 5  Split           ToCharArray         StringSplitOptions RemoveEmptyEntries       Join

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string sentence    This is a sentence with multiple    spaces   RegexOptions options   RegexOptions None  Regex regex   new Regex      2     options        sentence   regex Replace sentence

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Many answers are providing the right output but for those looking for the best performances  I did improve Nolanar s answer  which was the best answer for performance  by about 10    public static string MergeSpaces this string str         if  str    null                return null            else               StringBuilder stringBuilder   new StringBuilder str Length            int i   0          foreach  char c in str                        if  c           i    0    str i - 1                          stringBuilder Append c               i                      return stringBuilder ToString

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Old skool   string oldText       1 2  3   4    5        string newText   oldText                      Replace              char 22                        Replace   char 22                                  Replace   char 22              Assert That  newText  Is EqualTo    1 2 3 4 5

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Regex can be rather slow even with simple tasks   This creates an extension method that can be used off of any string               public static class StringExtension               public static String ReduceWhitespace this String value                        var newString   new StringBuilder                bool previousIsWhitespace   false              for  int i   0  i  lt  value Length  i                                  if  Char IsWhiteSpace value i                                          if  previousIsWhitespace                                                continue                                             previousIsWhitespace   true                                    else                                       previousIsWhitespace   false                                     newString Append value i                               return newString ToString                      It would be used as such   string testValue    This contains     too          much  whitespace   testValue   testValue ReduceWhitespace       testValue    This contains too much whitespace

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I like to use   myString   Regex Replace myString     s            Since it will catch runs of any kind of whitespace  e g  tabs  newlines  etc   and replace them with a single space

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string sentence    This is a sentence with multiple    spaces   RegexOptions options   RegexOptions None  Regex regex   new Regex      2     options        sentence   regex Replace sentence

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For those  who don t like Regex  here is a method that uses the StringBuilder       public static string FilterWhiteSpaces string input                if  input    null              return string Empty           StringBuilder stringBuilder   new StringBuilder input Length           for  int i   0  i  lt  input Length  i                          char c   input i               if  i    0    c            c         amp  amp  input i - 1                           stringBuilder Append c                     return stringBuilder ToString            In my tests  this method was 16 times faster on average with a very large set of small-to-medium sized strings  compared to a static compiled Regex  Compared to a non-compiled or non-static Regex  this should be even faster   Keep in mind  that it does not remove leading or trailing spaces  only multiple occurrences of such

User · Answer

I like to use   myString   Regex Replace myString     s            Since it will catch runs of any kind of whitespace  e g  tabs  newlines  etc   and replace them with a single space

User · Answer

This is a shorter version  which should only be used if you are only doing this once  as it creates a new instance of the Regex class every time it is called   temp   new Regex    2     Replace temp           If you are not too acquainted with regular expressions  here s a short explanation   The  2   makes the regex search for the character preceding it  and finds substrings between 2 and unlimited times  The  Replace temp       replaces all matches in the string temp with a space   If you want to use this multiple times  here is a better option  as it creates the regex IL at compile time   Regex singleSpacify   new Regex    2     RegexOptions Compiled   temp   singleSpacify Replace temp

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Mysample string string str   quot hi you           are          a demo quot      Split the words based on white sapce var demo  str  Split      Where s   gt   string IsNullOrWhiteSpace s               Join the values back and add a single space in between str   string Join  quot   quot   demo      output  string str   quot hi you are a demo quot

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string xyz    1   2   3   4   5   xyz   string Join       xyz Split  new char            StringSplitOptions RemoveEmptyEntries

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I just wrote a new Join that I like  so I thought I d re-answer  with it   public static string Join lt T gt  this IEnumerable lt T gt  source  string separator        return string Join separator  source Select e   gt  e ToString    ToArray         One of the cool things about this is that it work with collections that aren t strings  by calling ToString   on the elements   Usage is still the same          string s         1  2    4 5  Split           ToCharArray         StringSplitOptions RemoveEmptyEntries       Join

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Here is a slight modification on Nolonar original answer   Checking if the character is not just a space  but any whitespace  use this    It will replace any multiple whitespace character with a single space   public static string FilterWhiteSpaces string input        if  input    null          return string Empty       var stringBuilder   new StringBuilder input Length       for  int i   0  i  lt  input Length  i                  char c   input i           if  i    0     char IsWhiteSpace c      char IsWhiteSpace c   amp  amp                char IsWhiteSpace strValue i - 1                 stringBuilder Append c             return stringBuilder ToString

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Use the regex pattern                only space     var text   Regex Replace inputString

User · Answer

Another approach which uses LINQ    var list   str Split      Where s   gt   string IsNullOrWhiteSpace s     str   string Join      list

User · Answer

I like to use   myString   Regex Replace myString     s            Since it will catch runs of any kind of whitespace  e g  tabs  newlines  etc   and replace them with a single space

User · Answer

Here is a slight modification on Nolonar original answer   Checking if the character is not just a space  but any whitespace  use this    It will replace any multiple whitespace character with a single space   public static string FilterWhiteSpaces string input        if  input    null          return string Empty       var stringBuilder   new StringBuilder input Length       for  int i   0  i  lt  input Length  i                  char c   input i           if  i    0     char IsWhiteSpace c      char IsWhiteSpace c   amp  amp                char IsWhiteSpace strValue i - 1                 stringBuilder Append c             return stringBuilder ToString

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string sentence    This is a sentence with multiple    spaces   RegexOptions options   RegexOptions None  Regex regex   new Regex      2     options        sentence   regex Replace sentence

User · Answer

I know this is pretty old  but ran across this while trying to accomplish almost the same thing  Found this solution in RegEx Buddy  This pattern will replace all double spaces with single spaces and also trim leading and trailing spaces   pattern    m             2    replacement   1   Its a little difficult to read since we re dealing with empty space  so here it is again with the  spaces  replaced with a        pattern    m             2      lt -- don t use this  just for illustration    The    m   construct enables the  multi-line  option  I generally like to include whatever options I can within the pattern itself so it is more self contained

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myString   Regex Replace myString     2

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no Regex  no Linq    removes leading and trailing spaces as well as reducing any embedded multiple space segments to one space  string myString       0 1 2  3   4               5     myString   string Join      myString Split new char             StringSplitOptions RemoveEmptyEntries      result  0 1 2 3 4 5

User · Answer

Consolodating other answers  per Joel  and hopefully improving slightly as I go   You can do this with Regex Replace     string s   Regex Replace           1  2    4 5              2                       Or with String Split     static class StringExtensions       public static string Join this IList lt string gt  value  string separator                return string Join separator  value ToArray                     string s         1  2    4 5  Split           ToCharArray         StringSplitOptions RemoveEmptyEntries       Join

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string xyz    1   2   3   4   5   xyz   string Join       xyz Split  new char            StringSplitOptions RemoveEmptyEntries

User · Answer

Consolodating other answers  per Joel  and hopefully improving slightly as I go   You can do this with Regex Replace     string s   Regex Replace           1  2    4 5              2                       Or with String Split     static class StringExtensions       public static string Join this IList lt string gt  value  string separator                return string Join separator  value ToArray                     string s         1  2    4 5  Split           ToCharArray         StringSplitOptions RemoveEmptyEntries       Join

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Old skool   string oldText       1 2  3   4    5        string newText   oldText                      Replace              char 22                        Replace   char 22                                  Replace   char 22              Assert That  newText  Is EqualTo    1 2 3 4 5

[c#] How do I replace multiple spaces with a single space in C#?

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