C Version Of SQL LIKE

Question

Is there any way to search patterns in strings in C    Something like Sql LIKE would be very useful

User · Accepted Answer

Regular expressions allow for everything that LIKE allows for, and much more, but have a completely different syntax. However, since the rules for LIKE are so simple(where % means zero-or-more characters and _ means one character), and both LIKE arguments and regular expressions are expressed in strings, we can create a regular expression that takes a LIKE argument (e.g. abc_ef% *usd) and turn it into the equivalent regular expression (e.g. \Aabc.ef.* \*usd\z):

@"\A" + new Regex(@"\.|\$|\^|\{|\[|\(|\||\)|\*|\+|\?|\\").Replace(toFind, ch => @"\" + ch).Replace('_', '.').Replace("%", ".*") + @"\z"

From that we can build a Like() method:

public static class MyStringExtensions
{
  public static bool Like(this string toSearch, string toFind)
  {
    return new Regex(@"\A" + new Regex(@"\.|\$|\^|\{|\[|\(|\||\)|\*|\+|\?|\\").Replace(toFind, ch => @"\" + ch).Replace('_', '.').Replace("%", ".*") + @"\z", RegexOptions.Singleline).IsMatch(toSearch);
  }
}

And hence:

bool willBeTrue = "abcdefg".Like("abcd_fg");
bool willAlsoBeTrue = "abcdefg".Like("ab%f%");
bool willBeFalse = "abcdefghi".Like("abcd_fg");

User · Answer

As a late but proper answer   The closest thing there is to a SQL-Like function in C-Sharp is the implementation of a SQL-Like function in C    You can rip it out of  http   code google com p csharp-sqlite source checkout  root  csharp-sqlite Community CsharpSqlite src func c cs            Implementation of the like   SQL function   This function implements    the build-in LIKE operator   The first argument to the function is the    pattern and the second argument is the string   So  the SQL statements              A LIKE B       is implemented as like B A         This same function  with a different compareInfo structure  computes    the GLOB operator         static void likeFunc      sqlite3 context context      int argc      sqlite3 value   argv                   string zA  zB        u32 escape   0        int nPat        sqlite3 db   sqlite3 context db handle  context           zB   sqlite3 value text  argv 0           zA   sqlite3 value text  argv 1               Limit the length of the LIKE or GLOB pattern to avoid problems          of deep recursion and N N behavior in patternCompare                   nPat   sqlite3 value bytes  argv 0           testcase  nPat    db aLimit SQLITE LIMIT LIKE PATTERN LENGTH           testcase  nPat    db aLimit SQLITE LIMIT LIKE PATTERN LENGTH    1          if   nPat  gt  db aLimit SQLITE LIMIT LIKE PATTERN LENGTH                    sqlite3 result error  context   LIKE or GLOB pattern too complex   -1            return                  Debug Assert  zB    sqlite3 value text  argv 0           Encoding did not change           if   argc    3                      The escape character string must consist of a single UTF-8 character             Otherwise  return an error                     string zEsc   sqlite3 value text  argv 2             if   zEsc    null             return          if   sqlite3Utf8CharLen  zEsc  -1      1                       sqlite3 result error  context             ESCAPE expression must be a single character   -1              return                    escape   sqlite3Utf8Read  zEsc  ref zEsc                  if   zA    null  amp  amp  zB    null                   compareInfo pInfo    compareInfo sqlite3 user data  context     if SQLITE TEST  if  TCLSH         sqlite3 like count     else         sqlite3 like count iValue     endif  endif         sqlite3 result int  context  patternCompare  zB  zA  pInfo  escape     1   0                                    Compare two UTF-8 strings for equality where the first string can        potentially be a  glob  expression   Return true  1  if they        are the same and false  0  if they are different                Globbing rules                               Matches any sequence of zero or more characters                               Matches exactly one character                               Matches one character from the enclosed list of                       characters                               Matches one character not in the enclosed list                With the       and        matching  a     character can be included        in the list by making it the first character after     or       A        range of characters can be specified using  -    Example           a-z   matches any single lower-case letter   To match a  -   make        it the last character in the list                This routine is usually quick  but can be N  2 in the worst case                Hints  to match     or      put them in        Like this                        abc   xyz        Matches  abc xyz  only            static bool patternCompare      string zPattern                The glob pattern        string zString                 The string to compare against the glob        compareInfo pInfo              Information about how to do the compare        u32 esc                        The escape character                      u32 c  c2        int invert        int seen        int matchOne    int pInfo matchOne        int matchAll    int pInfo matchAll        int matchSet    int pInfo matchSet        bool noCase   pInfo noCase        bool prevEscape   false         True if the previous character was  escape           string inPattern   zPattern    Entered Pattern        while     c   sqlite3Utf8Read  zPattern  ref zPattern        0                   if    prevEscape  amp  amp  c    matchAll                       while     c   sqlite3Utf8Read  zPattern  ref zPattern        matchAll              c    matchOne                           if   c    matchOne  amp  amp  sqlite3Utf8Read  zString  ref zString      0                               return false                                      if   c    0                           return true                        else if   c    esc                           c   sqlite3Utf8Read  zPattern  ref zPattern                if   c    0                               return false                                      else if   c    matchSet                           Debug Assert  esc    0               This is GLOB  not LIKE                Debug Assert  matchSet  lt  0x80            is a single-byte character                int len   0              while   len  lt  zString Length  amp  amp  patternCompare  inPattern Substring  inPattern Length - zPattern Length - 1    zString Substring  len    pInfo  esc      false                               SQLITE SKIP UTF8  zString  ref len                              return len  lt  zString Length                        while     c2   sqlite3Utf8Read  zString  ref zString        0                           if   noCase                                if  0    c2  amp  0x7f                    c2    u32 sqlite3UpperToLower c2     GlogUpperToLower c2                  if   0        c    amp   0x7f                      c    u32 sqlite3UpperToLower c     GlogUpperToLower c                 while   c2    0  amp  amp  c2    c                                   c2   sqlite3Utf8Read  zString  ref zString                    if   0        c2    amp   0x7f                       c2    u32 sqlite3UpperToLower c2     GlogUpperToLower c2                                             else                             while   c2    0  amp  amp  c2    c                                   c2   sqlite3Utf8Read  zString  ref zString                                              if   c2    0                 return false              if   patternCompare  zPattern  zString  pInfo  esc                   return true                        return false                    else if    prevEscape  amp  amp  c    matchOne                       if   sqlite3Utf8Read  zString  ref zString      0                           return false                                else if   c    matchSet                       u32 prior c   0            Debug Assert  esc    0          This only occurs for GLOB  not LIKE              seen   0            invert   0            c   sqlite3Utf8Read  zString  ref zString              if   c    0               return false            c2   sqlite3Utf8Read  zPattern  ref zPattern              if   c2                                  invert   1              c2   sqlite3Utf8Read  zPattern  ref zPattern                          if   c2                                  if   c                        seen   1              c2   sqlite3Utf8Read  zPattern  ref zPattern                          while   c2    0  amp  amp  c2                                  if   c2     -   amp  amp  zPattern 0          amp  amp  zPattern 0     0  amp  amp  prior c  gt  0                               c2   sqlite3Utf8Read  zPattern  ref zPattern                  if   c  gt   prior c  amp  amp  c  lt   c2                   seen   1                prior c   0                            else                             if   c    c2                                   seen   1                                prior c   c2                            c2   sqlite3Utf8Read  zPattern  ref zPattern                          if   c2    0      seen   invert      0                           return false                                else if   esc    c  amp  amp   prevEscape                       prevEscape   true                    else                     c2   sqlite3Utf8Read  zString  ref zString              if   noCase                           if   c  lt  0x80                 c    u32 sqlite3UpperToLower c     GlogUpperToLower c               if   c2  lt  0x80                 c2    u32 sqlite3UpperToLower c2     GlogUpperToLower c2                         if   c    c2                           return false                        prevEscape   false                          return zString Length    0

User · Answer

As aready proposed in this answer and this other answer Microsoft VisualBasic CompilerServices Operators LikeString could be a good option for simple tasks  when a RegExp is overkill  Syntax is different from RegExp and SQL LIKE operator  but it s really simple to learn  mainly because it s also very limited    Assembly Microsoft VisualBasic must be added as a reference to the project to use this method   For more information see Operators LikeString Method and for a description of the syntax see Like Operator  Visual Basic    It can be used as an extension method to String class        lt summary gt      Visual Basic like operator  Performs simple  case insensitive  string pattern matching       lt  summary gt       lt param name  thisString  gt  lt  param gt       lt param name  pattern  gt      Any single character      Zero or more characters      Any single digit  0   9  lt  param gt       lt returns gt true if the string matches the pattern lt  returns gt  public static bool Like this string thisString  string pattern        gt  Microsoft VisualBasic CompilerServices Operators          LikeString thisString  pattern  Microsoft VisualBasic CompareMethod Text

User · Answer

Have your tried   This is a string  Contains  string

User · Answer

Linq to SQL Like Operator

User · Answer

Check out Regular Expressions

User · Answer

myString Contain  quot someString quot        equal with myString LIKE   someString   myString EndWith  quot someString quot        equal with myString LIKE   someString  myString StartWith  quot someString quot        equal with myString LIKE  someString

User · Answer

Use it like this   if  lbl Text StartWith  hr    true

User · Answer

This is my implementation - it passes the tests and does the trick - you may want to change the replacement token if you re using three tildes in your statements   private Regex LikeExpressionToRegexPattern String likePattern        var replacementToken               String result   likePattern Replace      replacementToken           Replace                  result   Regex Replace result            replacementToken                       result   result Replace replacementToken             return new Regex       result        RegexOptions IgnoreCase       Example      Define a test string  string text    Hello stackoverflow world    string like     flow        Define a regular expression and Find matches  MatchCollection matches   LikeExpressionToRegexPattern like  Matches text      Result  if  matches Count  gt  0          Yes   else         No

User · Answer

Simply  Contains   would do the work for you    Example String  Contains  amp        like   amp     This would return true  and performing a select on it would return the desired output

User · Answer

there are several good answers here   to summarize what is already here and correct  using contains  startswith  endswith are good answers for most needs   regular expressions are what you want for more advanced needs   something that is not mentioned in these answers  though  is that for a collection of strings  linq can be used to apply these filters in a call to the where method

User · Answer

When I ran into this on a contract  I had no other option than to have a 100  compliant TransactSQL LIKE function  Below is the result - a static function and a string extension method  I m sure it can be optimized further  but it s pretty fast and passed my long list of test scenarios  Hope it helps someone   using System  using System Collections Generic   namespace SqlLikeSample       public class TestSqlLikeFunction               static void Main string   args                        TestSqlLikePattern true                        TestSqlLikePattern true                         TestSqlLikePattern true        asdfa asdf asdf                TestSqlLikePattern true                         TestSqlLikePattern false                        TestSqlLikePattern true                         TestSqlLikePattern true        4                TestSqlLikePattern true        C                TestSqlLikePattern false        CX                TestSqlLikePattern false    ABCD                     TestSqlLikePattern true    ABCD     A                TestSqlLikePattern true    ABCD     b                TestSqlLikePattern false    ABCD     X                TestSqlLikePattern false    ABCD     AB                TestSqlLikePattern true    B-D     C                TestSqlLikePattern true    B-D     D                TestSqlLikePattern false    B-D     A                TestSqlLikePattern false     B-D     C                TestSqlLikePattern false     B-D     D                TestSqlLikePattern true     B-D     A                TestSqlLikePattern true    TEST ABCD XXX    lolTESTBXXX                TestSqlLikePattern false    TEST ABCD XXX    lolTESTZXXX                TestSqlLikePattern false    TEST  ABCD XXX    lolTESTBXXX                TestSqlLikePattern true    TEST  ABCD XXX    lolTESTZXXX                TestSqlLikePattern true    TEST B-D XXX    lolTESTBXXX                TestSqlLikePattern true    TEST  B-D XXX    lolTESTZXXX                TestSqlLikePattern true    Stuff txt   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true    Stuff  txt     MagicStuff txt                TestSqlLikePattern true    Stuff  txt     MagicStuff txt img                TestSqlLikePattern true    Stuff  txt     Stuff txt img                TestSqlLikePattern true    Stuff  txt     MagicStuff001 txt img                TestSqlLikePattern true    Stuff  txt     MagicStuff001 txt                TestSqlLikePattern true    Stuff  txt     1Stuff3 txt4                TestSqlLikePattern false    Stuff  txt     1Stuff txt4                TestSqlLikePattern false    Stuff  txt     1Stuff3 txt                TestSqlLikePattern false    Stuff  txt     Stuff3 txt4                 Console ReadKey                       public static void TestSqlLikePattern bool expectedResult  string pattern  string testString                        bool result   testString SqlLike pattern               if  expectedResult    result                                Console ForegroundColor   ConsoleColor Red  System Console Out Write   SqlLike  FAIL                              else                               Console ForegroundColor   ConsoleColor Green  Console Write   SqlLike  PASS                              Console ForegroundColor   ConsoleColor White  Console WriteLine          testString       LIKE       pattern              expectedResult                        public static class SqlLikeStringExtensions               public static bool SqlLike this string s  string pattern                        return SqlLikeStringUtilities SqlLike pattern  s                        public static class SqlLikeStringUtilities               public static bool SqlLike string pattern  string str                        bool isMatch   true                  isWildCardOn   false                  isCharWildCardOn   false                  isCharSetOn   false                  isNotCharSetOn   false                  endOfPattern   false              int lastWildCard   -1              int patternIndex   0              List lt char gt  set   new List lt char gt                 char p     0                for  int i   0  i  lt  str Length  i                                  char c   str i                   endOfPattern    patternIndex  gt   pattern Length                   if   endOfPattern                                        p   pattern patternIndex                        if   isWildCardOn  amp  amp  p                                                       lastWildCard   patternIndex                          isWildCardOn   true                          while  patternIndex  lt  pattern Length  amp  amp                              pattern patternIndex                                                                patternIndex                                                      if  patternIndex  gt   pattern Length  p     0                           else p   pattern patternIndex                                             else if  p                                                       isCharWildCardOn   true                          patternIndex                                              else if  p                                                       if  pattern   patternIndex                                                                isNotCharSetOn   true                              patternIndex                                                      else isCharSetOn   true                           set Clear                            if  pattern patternIndex   1      -   amp  amp  pattern patternIndex   3                                                                char start   char ToUpper pattern patternIndex                                patternIndex    2                              char end   char ToUpper pattern patternIndex                                if  start  lt   end                                                                for  char ci   start  ci  lt   end  ci                                                                          set Add ci                                                                                               patternIndex                                                       while  patternIndex  lt  pattern Length  amp  amp                              pattern patternIndex                                                                set Add pattern patternIndex                                patternIndex                                                      patternIndex                                                             if  isWildCardOn                                        if  char ToUpper c     char ToUpper p                                                 isWildCardOn   false                          patternIndex                                                            else if  isCharWildCardOn                                        isCharWildCardOn   false                                    else if  isCharSetOn    isNotCharSetOn                                        bool charMatch    set Contains char ToUpper c                         if   isNotCharSetOn  amp  amp  charMatch      isCharSetOn  amp  amp   charMatch                                                 if  lastWildCard  gt   0  patternIndex   lastWildCard                          else                                                       isMatch   false                              break                                                                      isNotCharSetOn   isCharSetOn   false                                    else                                       if  char ToUpper c     char ToUpper p                                                 patternIndex                                              else                                               if  lastWildCard  gt   0  patternIndex   lastWildCard                          else                                                       isMatch   false                              break                                                                                              endOfPattern    patternIndex  gt   pattern Length                if  isMatch  amp  amp   endOfPattern                                bool isOnlyWildCards   true                  for  int i   patternIndex  i  lt  pattern Length  i                                          if  pattern i                                                        isOnlyWildCards   false                          break                                                          if  isOnlyWildCards  endOfPattern   true                            return isMatch  amp  amp  endOfPattern

User · Answer

There are couple of ways you can search as  LIKE  operator of SQL in C   If you just want to know whether the pattern exists in the string variable  you can use   string value    samplevalue           value Contains  eva       like   eva            value StartsWith  eva        like  eva           value EndsWith  eva       like   eva    if you want to search the pattern from a list of string  you should use LINQ to Object Features               List lt string gt  valuee   new List lt string gt     samplevalue1    samplevalue2    samplevalue3             List lt string gt  contains    List lt string gt    from val in valuee                                         where val Contains  pattern                                           select val      like   pattern            List lt string gt  starts    List lt string gt    from val in valuee                                       where val StartsWith  pattern                                         select val     like  pattern            List lt string gt  ends    List lt string gt    from val in valuee                                                               where val EndsWith   pattern                                       select val     like   pattern

User · Answer

Operators LikeString  https   msdn microsoft com en-us library microsoft visualbasic compilerservices operators likestring v vs 100  ASPX  public static bool LikeString      string Source      string Pattern      CompareMethod CompareOption

User · Answer

I think you can use  a string Contains  str   for this   it will search in a string to a patern  and result true is founded and false if not

User · Answer

Contains maybe  if   bla bli blu  Contains  blu

User · Answer

Add a VB NET DLL encapsulating the VB NET Like Operator

User · Answer

public static bool Like this string value  string pattern        if  string IsNullOrEmpty value     string IsNullOrEmpty pattern           return false       bool valid   true      string   words   pattern Split  quot   quot        int counter   words Count         for  int i   0  i  lt  counter  i                  valid   valid  amp  amp  value StartsWith words i                            value   value Substring words i  Length             return valid

User · Answer

public static class StringsEx       public static IEnumerable lt String gt  Like this IEnumerable lt String gt  input  String pattern                var dt   new DataTable            dt Columns Add  Search            foreach  String str in input                        dt Rows Add str                     dt DefaultView RowFilter   String Format  Search LIKE   0     pattern           return dt DefaultView ToTable                AsEnumerable                Select r   gt  r Field lt String gt   Search               The only disadvantage is following   Wildcard characters are not allowed in the middle of a string  For example   te xt  is not allowed

User · Answer

Check out this question - How to do SQL Like   in Linq   Also  for more advanced string pattern searching  there are lots of tutorials on using Regular Expressions - e g  http   www codeproject com KB dotnet regextutorial aspx

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