How do I access named capturing groups in a NET Regex

Question

I m having a hard time finding a good resource that explains how to use Named Capturing Groups in C    This is the code that I have so far   string page   Encoding ASCII GetString bytePage   Regex qariRegex   new Regex   lt td gt  lt a href      lt link gt        gt    lt name gt      lt  a gt  lt  td gt     MatchCollection mc   qariRegex Matches page   CaptureCollection cc   mc 0  Captures  MessageBox Show cc 0  ToString       However this always just shows the full line    lt td gt  lt a href   path to file  gt Name of File lt  a gt  lt  td gt     I have experimented with several other  methods  that I ve found on various websites but I keep getting the same result   How can I access the named capturing groups that are specified in my regex

User · Accepted Answer

Use the group collection of the Match object  indexing it with the capturing group name  e g    foreach  Match m in mc       MessageBox Show m Groups  link   Value

User · Answer

This answers improves on Rashmi Pandit s answer  which is in a way better than the rest because that it seems to completely resolve the exact problem detailed in the question   The bad part is that is inefficient and not uses the IgnoreCase option consistently   Inefficient part is because regex can be expensive to construct and execute  and in that answer it could have been constructed just once  calling Regex IsMatch was just constructing the regex again behind the scene   And Match method could have been called only once and stored in a variable and then linkand name should call Result from that variable   And the IgnoreCase option was only used in the Match part but not in the Regex IsMatch part   I also moved the Regex definition outside the method in order to construct it just once  I think is the sensible approach if we are storing that the assembly with the RegexOptions Compiled option    private static Regex hrefRegex   new Regex   lt td gt   s  lt a  s href  s    s         lt link gt              lt link gt   S     s  gt    lt name gt      s  lt  a gt   s  lt  td gt     RegexOptions IgnoreCase   RegexOptions Compiled    public static bool TryGetHrefDetails string htmlTd  out string link  out string name        var matches   hrefRegex Match htmlTd       if  matches Success                link   matches Result    link             name   matches Result    name             return true            else               link   null          name   null          return false

User · Answer

The following code sample  will match the pattern even in case of space characters in between  i e       lt td gt  lt a href   path to file  gt Name of File lt  a gt  lt  td gt    as well as    lt td gt   lt a      href   path to file   gt Name of File lt  a gt    lt  td gt    Method returns true or false  depending on whether the input htmlTd string matches the pattern or no  If it matches  the out params contain the link and name respectively        lt summary gt      Assigns proper values to link and name  if the htmlId matches the pattern      lt  summary gt       lt returns gt true if success  false otherwise lt  returns gt  public static bool TryGetHrefDetails string htmlTd  out string link  out string name        link   null      name   null       string pattern     lt td gt   s  lt a  s href  s    s         lt link gt              lt link gt   S     s  gt    lt name gt      s  lt  a gt   s  lt  td gt         if  Regex IsMatch htmlTd  pattern                 Regex r   new Regex pattern   RegexOptions IgnoreCase   RegexOptions Compiled           link   r Match htmlTd  Result    link             name   r Match htmlTd  Result    name             return true            else         return false      I have tested this and it works correctly

User · Answer

Additionally if someone have a use case where he needs group names before executing search on Regex object he can use   var regex   new Regex pattern      initialized somewhere        var groupNames   regex GetGroupNames

User · Answer

You specify the named capture group string by passing it to the indexer of the Groups property of a resulting Match object   Here is a small example   using System  using System Text RegularExpressions   class Program       static void Main                 String sample    hello-world-           Regex regex   new Regex  -   lt test gt   -   -             Match match   regex Match sample            if  match Success                        Console WriteLine match Groups  test   Value

[c#] How do I access named capturing groups in a .NET Regex?

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