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Regular Expression

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Regular Expression Miscellaneous Constructs
  .NET Miscellaneous Constructs
   Inline Options
   Inline Comment
   End-of-Line Comment
 See also

Regular Expression Miscellaneous Constructs

Regular expressions in .NET include three miscellaneous language constructs. One lets you enable or disable particular matching options in the middle of a regular expression pattern. The remaining two let you include comments in a regular expression.

.NET Miscellaneous Constructs

Inline Options

You can set or disable specific pattern matching options for part of a regular expression by using the syntax


You list the options you want to enable after the question mark, and the options you want to disable after the minus sign. The following table describes each option. For more information about each option, see Regular Expression Options.

Option Description
i Case-insensitive matching.
m Multiline mode.
n Explicit captures only. (Parentheses do not act as capturing groups.)
s Single-line mode.
x Ignore unescaped white space, and allow x-mode comments.

Any change in regular expression options defined by the (?imnsx-imnsx) construct remains in effect until the end of the enclosing group.

The (?imnsx-imnsx:subexpression) grouping construct provides identical functionality for a subexpression. For more information, see Grouping Constructs.

Inline Comment

The (?# comment) construct lets you include an inline comment in a regular expression. The regular expression engine does not use any part of the comment in pattern matching, although the comment is included in the string that is returned by the Regex.ToString method. The comment ends at the first closing parenthesis.

End-of-Line Comment

A number sign (#)marks an x-mode comment, which starts at the unescaped # character at the end of the regular expression pattern and continues until the end of the line. To use this construct, you must either enable the x option (through inline options) or supply the RegexOptions.IgnorePatternWhitespace value to the option parameter when instantiating the Regex object or calling a static Regex method.

Note that, instead of providing the (?x) construct in the regular expression, the comment could also have been recognized by calling the Regex.IsMatch(String, String, RegexOptions) method and passing it the RegexOptions.IgnorePatternWhitespace enumeration value.


Examples of Miscellaneous Constructs

<%@ Page Language="VB" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "">
       <title>Sample Page</title>
       <meta http-equiv="Content-Type" content="text/html;charset=utf-8">
       <script runat="server">
           Sub Page_Load()
               Dim xstring As String = "zabcd fg ijaab"
               Dim xmatchstr As String = ""
               xmatchstr = xmatchstr & "Given string: """ & xstring & """<br />"
               xmatchstr = xmatchstr & showresult(xstring,"(?i)(\w)(\w).+F")
               xmatchstr = xmatchstr & showresult(xstring,"((?#comment)\w)(\w).+f")
               xmatchstr = xmatchstr & showresult(xstring,"(?x)(\w)(\w).+ # comment")
               lbl01.Text = xmatchstr
           End Sub
           Function showresult(xstring,xpattern)
               Dim xmatch As Match
               Dim xcaptures As CaptureCollection
               Dim ycaptures As CaptureCollection
               Dim xgroups As GroupCollection
               Dim xmatchstr As String = ""
               Dim xint As Integer
               Dim yint As Integer
               Dim zint As Integer
               xmatchstr = xmatchstr & "<br />Result of Regex.Match(string,""" & Replace(xpattern,"<","&lt;") & """): """
               xmatch = Regex.Match(xstring,xpattern)
               xmatchstr = xmatchstr & xmatch.value & """<br />"
               xcaptures = xmatch.Captures
               xmatchstr = xmatchstr & "->Result of CaptureCollection.Count: """
               xmatchstr = xmatchstr & xcaptures.Count & """<br />"
               For xint = 0 to xcaptures.Count - 1
                   xmatchstr = xmatchstr & "->->Result of CaptureCollection("& xint & ").Value, Index, Length: """
                   xmatchstr = xmatchstr & xcaptures(xint).Value & ", " & xcaptures(xint).Index & ", " & xcaptures(xint).Length & """<br />"
                   xgroups = xmatch.Groups
                   xmatchstr = xmatchstr & "->Result of GroupCollection.Count: """
                   xmatchstr = xmatchstr & xgroups.Count & """<br />"
                   For yint = 0 to xgroups.Count - 1
                       xmatchstr = xmatchstr & "->->Result of GroupCollection("& yint & ").Value, Index, Length: """
                       xmatchstr = xmatchstr & xgroups(yint).Value & ", " & xgroups(yint).Index & ", " & xgroups(yint).Length & """<br />"
                       ycaptures = xgroups(yint).Captures
                       xmatchstr = xmatchstr & "->->->Result of CaptureCollection.Count: """
                       xmatchstr = xmatchstr & ycaptures.Count & """<br />"
                       For zint = 0 to ycaptures.Count - 1
                           xmatchstr = xmatchstr & "->->->->Result of CaptureCollection("& zint & ").Value, Index, Length: """
                           xmatchstr = xmatchstr & ycaptures(zint).Value & ", " & ycaptures(zint).Index & ", " & ycaptures(zint).Length & """<br />"
               Return xmatchstr
           End Function
       <% Response.Write ("<h1>This is a Sample Page of Miscellaneous Constructs</h1>") %>
           <%-- Set on Page_Load --%>
           <asp:Label id="lbl01" runat="server" />
HTML Web Page Embedded Output:

See also

  • Regular Expression Language - Quick Reference





  1. Active Server Pages,, updated 20Dec2012
  2. ASP Overview,, updated 21Dec2012
  3. ASP Best Practices,, updated 15Apr2013
  4. ASP Built-in Objects,, updated 20Dec2012
  5. Response Object,, updated 20Dec2012
  6. Request Object,, updated 20Dec2012
  7. Server Object (IIS),, updated 20Dec2012
  8. Application Object (IIS),, updated 20Dec2012
  9. Session Object (IIS),, updated 20Dec2012
  10. ASPError Object,, updated 20Dec2012
  11. ObjectContext Object (IIS),, updated 20Dec2012
  12. Debugging Global.asa Files,, updated 15Apr2013
  13. How to: Debug Global.asa files,, updated 15Apr2013
  14. Calling COM Components from ASP Pages,, updated 15Apr2013
  15. IIS ASP Scripting Reference,, updated 15Apr2013
  16. ASP Keywords,, updated 15Apr2013
  17. Creating Simple ASP Pages,, updated 15Apr2013
  18. Including Files in ASP Applications,, updated 15Apr2013
  19. ASP Overview,, updated 15Apr2013
  20. FileSystemObject Object,, updated 14Mayr2013
  21., ADO Object Model, updated 15Apr2013
  22. ADO Fundamentals,, updated 14Mayr2013

ID: 190800003 Last Updated: 2019/8/3 Revision: Ref:


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