URL Encoding using C

Question

I have an application which sends a POST request to the VB forum software and logs someone in  without setting cookies or anything    Once the user is logged in I create a variable that creates a path on their local machine   c  tempfolder date username  The problem is that some usernames are throwing  Illegal chars  exception  For example if my username was mas fenix it would throw an exception    Path Combine            Environment GetFolderPath System Environment SpecialFolder CommonApplicationData       DateTime Now ToString  ddMMyyhhmm      -    form1 username    I don t want to remove it from the string  but a folder with their username is created through FTP on a server  And this leads to my second question  If I am creating a folder on the server can I leave the  illegal chars  in  I only ask this because the server is Linux based  and I am not sure if Linux accepts it or not   EDIT  It seems that URL encode is NOT what I want   Here s what I want to do   old username   mas fenix new username   mas xxfenix   Where  xx is the ASCII value or any other value that would easily identify the character

User · Accepted Answer

Edit  Note that this answer is now out of date  See Siarhei Kuchuk s answer below for a better fix  UrlEncoding will do what you are suggesting here  With C   you simply use HttpUtility  as mentioned    You can also Regex the illegal characters and then replace  but this gets far more complex  as you will have to have some form of state machine  switch     case  for example  to replace with the correct characters  Since UrlEncode does this up front  it is rather easy   As for Linux versus windows  there are some characters that are acceptable in Linux that are not in Windows  but I would not worry about that  as the folder name can be returned by decoding the Url string  using UrlDecode  so you can round trip the changes

User · Answer

If you can t see System Web  change your project settings  The target framework should be   NET Framework 4  instead of   NET Framework 4 Client Profile

User · Answer

Better way is to use  Uri EscapeUriString  to not reference Full Profile of  net 4

User · Answer

You should encode only the user name or other part of the URL that could be invalid  URL encoding a URL can lead to problems since something like this   string url   HttpUtility UrlEncode  http   www google com search q Example      Will yield       http 3a 2f 2fwww google com 2fsearch 3fq 3dExample   This is obviously not going to work well  Instead  you should encode ONLY the value of the key value pair in the query string  like this   string url    http   www google com search q     HttpUtility UrlEncode  Example      Hopefully that helps  Also  as teedyay mentioned  you ll still need to make sure illegal file-name characters are removed or else the file system won t like the path

User · Answer

Levi Botelho commented that the table of encodings that was previously generated is no longer accurate for  NET 4 5  since the encodings changed slightly between  NET 4 0 and 4 5   So I ve regenerated the table for  NET 4 5   Unencoded UrlEncoded UrlEncodedUnicode UrlPathEncoded WebUtilityUrlEncoded EscapedDataString EscapedUriString HtmlEncoded HtmlAttributeEncoded WebUtilityHtmlEncoded HexEscaped A         A          A                 A              A                    A                 A                A           A                    A                      41 B         B          B                 B              B                    B                 B                B           B                    B                      42  a         a          a                 a              a                    a                 a                a           a                    a                      61 b         b          b                 b              b                    b                 b                b           b                    b                      62  0         0          0                 0              0                    0                 0                0           0                    0                      30 1         1          1                 1              1                    1                 1                1           1                    1                      31   space                                  20                                  20                20               space       space                space                 20                                                                             21                                                                                        21            22         22                               22                   22                22               amp quot        amp quot                 amp quot                  22            23         23                               23                   23                                                                                        23            24         24                               24                   24                                                                                        24            25         25                               25                   25                25                                                                      25  amp           26         26                amp                26                   26                amp                  amp amp         amp amp                  amp amp                   26            27         27                               27                   27                                 amp  39         amp  39                  amp  39                   27                                                                             28                                                                                        28                                                                             29                                                                                        29                                                                             2A                                                                                        2A            2b         2b                               2B                   2B                                                                                        2B            2c         2c                               2C                   2C                                                                                        2C -         -          -                 -              -                    -                 -                -           -                    -                      2D                                                                                                                                                                       2E            2f         2f                               2F                   2F                                                                                        2F            3a         3a                               3A                   3A                                                                                        3A            3b         3b                               3B                   3B                                                                                        3B  lt           3c         3c                lt                3C                   3C                3C               amp lt          amp lt                   amp lt                    3C            3d         3d                               3D                   3D                                                                                        3D  gt           3e         3e                gt                3E                   3E                3E               amp gt          gt                      amp gt                    3E            3f         3f                               3F                   3F                                                                                        3F            40         40                               40                   40                                                                                        40            5b         5b                               5B                   5B                                                                                        5B            5c         5c                               5C                   5C                5C                                                                      5C            5d         5d                               5D                   5D                                                                                        5D            5e         5e                               5E                   5E                5E                                                                      5E                                                                                                                                                                       5F            60         60                               60                   60                60                                                                      60            7b         7b                               7B                   7B                7B                                                                      7B            7c         7c                               7C                   7C                7C                                                                      7C            7d         7d                               7D                   7D                7D                                                                      7D            7e         7e                               7E                                                                                                             7E  A          c4 80      u0100             c4 80          C4 80                C4 80             C4 80           A           A                    A                      OoR  a          c4 81      u0101             c4 81          C4 81                C4 81             C4 81           a           a                    a                      OoR  E          c4 92      u0112             c4 92          C4 92                C4 92             C4 92           E           E                    E                      OoR  e          c4 93      u0113             c4 93          C4 93                C4 93             C4 93           e           e                    e                      OoR  I          c4 aa      u012a             c4 aa          C4 AA                C4 AA             C4 AA           I           I                    I                      OoR  i          c4 ab      u012b             c4 ab          C4 AB                C4 AB             C4 AB           i           i                    i                      OoR  O          c5 8c      u014c             c5 8c          C5 8C                C5 8C             C5 8C           O           O                    O                      OoR  o          c5 8d      u014d             c5 8d          C5 8D                C5 8D             C5 8D           o           o                    o                      OoR  U          c5 aa      u016a             c5 aa          C5 AA                C5 AA             C5 AA           U           U                    U                      OoR  u          c5 ab      u016b             c5 ab          C5 AB                C5 AB             C5 AB           u           u                    u                      OoR    The columns represent encodings as follows    UrlEncoded  HttpUtility UrlEncode UrlEncodedUnicode  HttpUtility UrlEncodeUnicode UrlPathEncoded  HttpUtility UrlPathEncode WebUtilityUrlEncoded  WebUtility UrlEncode EscapedDataString  Uri EscapeDataString    EscapedUriString  Uri EscapeUriString    HtmlEncoded  HttpUtility HtmlEncode    HtmlAttributeEncoded  HttpUtility HtmlAttributeEncode    WebUtilityHtmlEncoded  WebUtility HtmlEncode    HexEscaped  Uri HexEscape   NOTES     HexEscape can only handle the first 255 characters   Therefore it throws an ArgumentOutOfRange exception for the Latin A-Extended characters  eg A   This table was generated in  NET 4 5  see answer https   stackoverflow com a 11236038 216440 for the encodings relevant to  NET 4 0 and below     EDIT     As a result of Discord s answer I added the new WebUtility UrlEncode and HtmlEncode methods  which were introduced in  NET 4 5

User · Answer

Ideally these would go in a class called  FileNaming  or maybe just rename Encode to  FileNameEncode   Note  these are not designed to handle Full Paths  just the folder and or file names   Ideally you would Split      your full path first and then check the pieces  And obviously instead of a union  you could just add the     character to the list of chars not allowed in Windows  but I think it s more helpful readable factual this way  Decode   is exactly the same but switches the Replace Uri HexEscape s 0    s   escaped  with the character   public static List lt string gt  urlEncodedCharacters   new List lt string gt                   lt      gt                               and others  but not        Since this is a superset of urlEncodedCharacters  we won t be able to only use UrlEncode   - instead we ll use HexEncode public static List lt string gt  specialCharactersNotAllowedInWindows   new List lt string gt                   lt      gt                               windows dissallowed character set         public static string Encode string fileName                  CheckForFullPath fileName      optional  make sure it s not a path          List lt string gt  charactersToChange   new List lt string gt  specialCharactersNotAllowedInWindows           charactersToChange AddRange urlEncodedCharacters              Where x   gt   urlEncodedCharacters Union specialCharactersNotAllowedInWindows  Contains x          add any non duplicates              charactersToChange ForEach s   gt  fileName   fileName Replace s  Uri HexEscape s 0                 gt    3f           return fileName          Thanks  simon-tewsi for the very usefull table above

User · Answer

The  NET implementation of UrlEncode does not comply with RFC 3986     Some characters are not encoded but should be  The      characters are listed in the RFC s section 2 2 as a reserved characters that must be encoded yet  NET fails to encode these characters  Some characters are encoded but should not be  The  -  characters are not listed in the RFC s section 2 2 as a reserved character that should not be encoded yet  NET erroneously encodes these characters  The RFC specifies that to be consistent  implementations should use upper-case HEXDIG  where  NET produces lower-case HEXDIG

User · Answer

Url Encoding is easy in  NET  Use   System Web HttpUtility UrlEncode string url    If that ll be decoded to get the folder name  you ll still need to exclude characters that can t be used in folder names           etc

User · Answer

I think people here got sidetracked by the UrlEncode message   URLEncoding is not what you want -- you want to encode stuff that won t work as a filename on the target system   Assuming that you want some generality -- feel free to find the illegal characters on several systems  MacOS  Windows  Linux and Unix   union them to form a set of characters to escape   As for the escape  a HexEscape should be fine  Replacing the characters with  XX   Convert each character to UTF-8 bytes and encode everything  128 if you want to support systems that don t do unicode   But there are other ways  such as using back slashes     or HTML encoding   quot     You can create your own   All any system has to do is  encode  the uncompatible character away   The above systems allow you to recreate the original name -- but something like replacing the bad chars with spaces works also   On the same tangent as above  the only one to use is      Uri EscapeDataString   -- It encodes everything that is needed for OAuth  it doesn t encode the things that OAuth forbids encoding  and encodes the space as  20 and not    Also in the OATH Spec   See  RFC 3986   AFAIK  this is the latest URI spec

User · Answer

I have written a C  method that url-encodes ALL symbols            lt summary gt             345Hf     21 23 24 33 34 35 48 66 7D          lt  summary gt      public static string UrlEncodeExtended  string value                 char   chars   value ToCharArray            StringBuilder encodedValue   new StringBuilder            foreach  char c in chars                        encodedValue Append           int c   ToString   X2                         return encodedValue ToString

User · Answer

In addition to  Dan Herbert s answer    You we should encode just the values generally   Split has params parameter Split   amp         expression firstly split by  amp  then     so odd elements are all values to be encoded shown below   public static void EncodeQueryString ref string queryString        var array queryString Split   amp             for  int i   0  i  lt  array Length  i              string part array i           if i 2  1                                       part System Web HttpUtility UrlEncode array i                queryString queryString Replace array i  part

User · Answer

Since  NET Framework 4 5 and  NET Standard 1 0 you should use WebUtility UrlEncode  Advantages over alternatives    It is part of  NET Framework 4 5    NET Core 1 0    NET Standard 1 0   UWP 10 0  and all Xamarin platforms as well  HttpUtility  while being available in  NET Framework earlier   NET  Framework 1 1    becomes available on other platforms much later   NET  Core 2 0    NET  Standard 2 0   and it still unavailable in UWP  see related question   In  NET Framework  it resides in System dll  so it does not require any additional references  unlike HttpUtility  It properly escapes characters for URLs  unlike Uri EscapeUriString  see comments to drweb86 s answer   It does not have any limits on the length of the string  unlike Uri EscapeDataString  see related question   so it can be used for POST requests  for example

User · Answer

I ve been experimenting with the various methods  NET provide for URL encoding   Perhaps the following table will be useful  as output from a test app I wrote    Unencoded UrlEncoded UrlEncodedUnicode UrlPathEncoded EscapedDataString EscapedUriString HtmlEncoded HtmlAttributeEncoded HexEscaped A         A          A                 A              A                 A                A           A                     41 B         B          B                 B              B                 B                B           B                     42  a         a          a                 a              a                 a                a           a                     61 b         b          b                 b              b                 b                b           b                     62  0         0          0                 0              0                 0                0           0                     30 1         1          1                 1              1                 1                1           1                     31   space                                  20             20                20               space       space                20                                                                                                                            21            22         22                               22                22               amp quot        amp quot                 22            23         23                               23                                                                  23            24         24                               24                                                                  24            25         25                               25                25                                                25  amp           26         26                amp                26                amp                  amp amp         amp amp                  26            27         27                                                                  amp  39         amp  39                  27                                                                                                                            28                                                                                                                            29                                                        2A                                                                  2A            2b         2b                               2B                                                                  2B            2c         2c                               2C                                                                  2C -         -          -                 -              -                 -                -           -                     2D                                                                                                                            2E            2f         2f                               2F                                                                  2F            3a         3a                               3A                                                                  3A            3b         3b                               3B                                                                  3B  lt           3c         3c                lt                3C                3C               amp lt          amp lt                   3C            3d         3d                               3D                                                                  3D  gt           3e         3e                gt                3E                3E               amp gt          gt                      3E            3f         3f                               3F                                                                  3F            40         40                               40                                                                  40            5b         5b                               5B                5B                                                5B            5c         5c                               5C                5C                                                5C            5d         5d                               5D                5D                                                5D            5e         5e                               5E                5E                                                5E                                                                                                                            5F            60         60                               60                60                                                60            7b         7b                               7B                7B                                                7B            7c         7c                               7C                7C                                                7C            7d         7d                               7D                7D                                                7D            7e         7e                                                                                                   7E  A          c4 80      u0100             c4 80          C4 80             C4 80           A           A                     OoR  a          c4 81      u0101             c4 81          C4 81             C4 81           a           a                     OoR  E          c4 92      u0112             c4 92          C4 92             C4 92           E           E                     OoR  e          c4 93      u0113             c4 93          C4 93             C4 93           e           e                     OoR  I          c4 aa      u012a             c4 aa          C4 AA             C4 AA           I           I                     OoR  i          c4 ab      u012b             c4 ab          C4 AB             C4 AB           i           i                     OoR  O          c5 8c      u014c             c5 8c          C5 8C             C5 8C           O           O                     OoR  o          c5 8d      u014d             c5 8d          C5 8D             C5 8D           o           o                     OoR  U          c5 aa      u016a             c5 aa          C5 AA             C5 AA           U           U                     OoR  u          c5 ab      u016b             c5 ab          C5 AB             C5 AB           u           u                     OoR    The columns represent encodings as follows    UrlEncoded  HttpUtility UrlEncode UrlEncodedUnicode  HttpUtility UrlEncodeUnicode UrlPathEncoded  HttpUtility UrlPathEncode EscapedDataString  Uri EscapeDataString EscapedUriString  Uri EscapeUriString HtmlEncoded  HttpUtility HtmlEncode HtmlAttributeEncoded  HttpUtility HtmlAttributeEncode HexEscaped  Uri HexEscape   NOTES     HexEscape can only handle the first 255 characters   Therefore it throws an ArgumentOutOfRange exception for the Latin A-Extended characters  eg A   This table was generated in  NET 4 0  see Levi Botelho s comment below that says the encoding in  NET 4 5 is slightly different     EDIT   I ve added a second table with the encodings for  NET 4 5   See this answer  https   stackoverflow com a 21771206 216440  EDIT 2   Since people seem to appreciate these tables  I thought you might like the source code that generates the table  so you can play around yourselves   It s a simple C  console application  which can target either  NET 4 0 or 4 5   using System  using System Collections Generic  using System Text     Need to add a Reference to the System Web assembly  using System Web   namespace UriEncodingDEMO2       class Program               static void Main string   args                        EncodeStrings                 Console WriteLine                Console WriteLine  Press any key to continue                   Console Read                       public static void EncodeStrings                         string stringToEncode    ABCD     abcd                 0123             amp       -     lt   gt                   AaEeIiOoUu                   Need to set the console encoding to display non-ASCII characters correctly  eg the                  Latin A-Extended characters such as AaEe                  Console OutputEncoding   Encoding UTF8                  Will also need to set the console font  in the console Properties dialog  to a font                  that displays the extended character set correctly                 The following fonts all display the extended characters correctly                  Consolas                 DejaVu Sana Mono                 Lucida Console                 Also  in the console Properties  set the Screen Buffer Size and the Window Size                  Width properties to at least 140 characters  to display the full width of the                  table that is generated               Dictionary lt string  Func lt string  string gt  gt  columnDetails                   new Dictionary lt string  Func lt string  string gt  gt                 columnDetails Add  Unencoded    unencodedString   gt  unencodedString                columnDetails Add  UrlEncoded                    unencodedString   gt  HttpUtility UrlEncode unencodedString                 columnDetails Add  UrlEncodedUnicode                    unencodedString   gt  HttpUtility UrlEncodeUnicode unencodedString                 columnDetails Add  UrlPathEncoded                    unencodedString   gt  HttpUtility UrlPathEncode unencodedString                 columnDetails Add  EscapedDataString                    unencodedString   gt  Uri EscapeDataString unencodedString                 columnDetails Add  EscapedUriString                    unencodedString   gt  Uri EscapeUriString unencodedString                 columnDetails Add  HtmlEncoded                    unencodedString   gt  HttpUtility HtmlEncode unencodedString                 columnDetails Add  HtmlAttributeEncoded                    unencodedString   gt  HttpUtility HtmlAttributeEncode unencodedString                 columnDetails Add  HexEscaped                    unencodedString                       gt                                                   Uri HexEscape can only handle the first 255 characters so for the                              Latin A-Extended characters  such as A  it will throw an                              ArgumentOutOfRange exception                                                 try                                                       return Uri HexEscape unencodedString ToCharArray   0                                                      catch                                                       return   OoR                                                                    char   charactersToEncode   stringToEncode ToCharArray                string   stringCharactersToEncode   Array ConvertAll lt char  string gt  charactersToEncode                   character   gt  character ToString                  DisplayCharacterTable lt string gt  stringCharactersToEncode  columnDetails                      private static void DisplayCharacterTable lt TUnencoded gt  TUnencoded   unencodedArray              Dictionary lt string  Func lt TUnencoded  string gt  gt  mappings                        foreach  string key in mappings Keys                                Console Write key Replace        space                                      Console WriteLine                 foreach  TUnencoded unencodedObject in unencodedArray                                string stringCharToEncode   unencodedObject ToString                    foreach  string columnHeader in mappings Keys                                        int columnWidth   columnHeader Length   1                      Func lt TUnencoded  string gt  encoder   mappings columnHeader                       string encodedString   encoder unencodedObject                           ASSUMPTION  Column header will always be wider than encoded string                      Console Write encodedString Replace        space    PadRight columnWidth                                      Console WriteLine

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