How do I remove all non alphanumeric characters from a string except dash

Question

How do I remove all non alphanumeric characters from a string except dash and space characters

User · Answer

Using System Linq  string withOutSpecialCharacters   new string stringWithSpecialCharacters Where c   gt char IsLetterOrDigit c     char IsWhiteSpace c     c     -   ToArray

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The regex is    w s -      s is better to use instead of space     because there might be a tab in the text

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I use a variation of one of the answers here  I want to replace spaces with  -  so its SEO friendly and also make lower case  Also not reference system web from my services layer   private string MakeUrlString string input        var array   input ToCharArray         array   Array FindAll lt char gt  array  c   gt  char IsLetterOrDigit c     char IsWhiteSpace c     c     -         var newString   new string array  Replace       -   ToLower        return newString

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There is a much easier way with Regex    private string FixString string str        return string IsNullOrEmpty str    str   Regex Replace str      D

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Want something quick   public static class StringExtensions        public static string ToAlphaNumeric this string self  params char   allowedCharacters                return new string Array FindAll self ToCharArray    c   gt  char IsLetterOrDigit c     allowedCharacters Contains c               This will allow you to specify which characters you want to allow as well

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You can try   string s1   Regex Replace s     A-Za-z0-9 -           Where s is your string

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Replace   a-zA-Z0-9 -  with an empty string   Regex rgx   new Regex    a-zA-Z0-9 -     str   rgx Replace str

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Here is a non-regex heap allocation friendly fast solution which was what I was looking for   Unsafe edition   public static unsafe void ToAlphaNumeric ref string input        fixed  char  p   input                int offset   0          for  int i   0  i  lt  input Length  i                          if  char IsLetterOrDigit p i                                  p offset    input i                   offset                                      int  p  -1    offset     Changes the length of the string         p offset      0             And for those who don t want to use unsafe or don t trust the string length hack   public static string ToAlphaNumeric string input        int j   0      char   newCharArr   new char input Length        for  int i   0  i  lt  input Length  i                  if  char IsLetterOrDigit input i                          newCharArr j    input i               j                         Array Resize ref newCharArr  j        return new string newCharArr

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I  ve made a different solution  by eliminating the Control characters  which was my original problem   It is better than putting in a list all the  special but good  chars  char   arr   str Where c   gt   char IsControl c   ToArray        str   new string arr     it  s simpler  so I think it  s better

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I could have used RegEx  they can provide elegant solution but they can cause performane issues  Here is one solution  char   arr   str ToCharArray     arr   Array FindAll lt char gt  arr   c   gt   char IsLetterOrDigit c                                        char IsWhiteSpace c                                        c     -      str   new string arr       When using the compact framework  which doesn t have FindAll   Replace FindAll with1  char   arr   str Where c   gt   char IsLetterOrDigit c                                   char IsWhiteSpace c                                   c     -    ToArray      str   new string arr       1 Comment by ShawnFeatherly

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Based on the answer for this question  I created a static class and added these  Thought it might be useful for some people   public static class RegexConvert       public static string ToAlphaNumericOnly this string input                Regex rgx   new Regex    a-zA-Z0-9             return rgx Replace input                  public static string ToAlphaOnly this string input                Regex rgx   new Regex    a-zA-Z             return rgx Replace input                  public static string ToNumericOnly this string input                Regex rgx   new Regex    0-9             return rgx Replace input                 Then the methods can be used as   string example    asdf1234       string alphanumeric   example ToAlphaNumericOnly    string alpha   example ToAlphaOnly    string numeric   example ToNumericOnly

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If you are working in JS  here is a very terse version myString   myString replace    A-Za-z0-9 -  g   quot  quot

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Here s an extension method using  ata answer as inspiration    hello-world123  456  MakeAlphaNumeric new char    -       yields  hello-world123456    or if you require additional characters other than hyphen      hello-world123  456    MakeAlphaNumeric new char    -           yields  hello-world123456     public static class StringExtensions          public static string MakeAlphaNumeric this string input  params char   exceptions                var charArray   input ToCharArray            var alphaNumeric   Array FindAll lt char gt  charArray   c   gt  char IsLetterOrDigit c    exceptions  Contains c     true            return new string alphaNumeric

[c#] How do I remove all non alphanumeric characters from a string except dash?

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