Match Class

Definition

Namespace:

System.Text.RegularExpressions

Assembly:

System.Text.RegularExpressions.dll

Source:

Match.cs

Represents the results from a single regular expression match.

public ref class Match : System::Text::RegularExpressions::Group

public class Match : System.Text.RegularExpressions.Group

type Match = class
    inherit Group

Public Class Match
Inherits Group

Inheritance

Object

Capture

Group

Match

Examples

The following examples use the regular expression Console\.Write(Line)?. The regular expression is interpreted as follows:

Console\.Write	Match the string "Console.Write". Note that the "." character is escaped so that it is interpreted as a literal period rather than as a wildcard that matches any character.
(Line)?	Match zero or one occurrence of the string "Line".

Example 1

The following example calls the Regex.Matches(String, String) method to retrieve all pattern matches in an input string. It then iterates the Match objects in the returned MatchCollection object to display information about each match.

using System;
using System.Text.RegularExpressions;

public class Example
{
   public static void Main()
   {
      string input = "int[] values = { 1, 2, 3 };\n" +
                     "for (int ctr = values.GetLowerBound(1); ctr <= values.GetUpperBound(1); ctr++)\n" +
                     "{\n" +
                     "   Console.Write(values[ctr]);\n" +
                     "   if (ctr < values.GetUpperBound(1))\n" +
                     "      Console.Write(\", \");\n" +
                     "}\n" +
                     "Console.WriteLine();\n";   
      
      string pattern = @"Console\.Write(Line)?";
      MatchCollection matches = Regex.Matches(input, pattern);
      foreach (Match match in matches)
         Console.WriteLine("'{0}' found in the source code at position {1}.",  
                           match.Value, match.Index);
   }
}
// The example displays the following output:
//    'Console.Write' found in the source code at position 112.
//    'Console.Write' found in the source code at position 184.
//    'Console.WriteLine' found in the source code at position 207.

Imports System.Text.RegularExpressions

Module Example
   Public Sub Main()
      Dim input As String = "Dim values() As Integer = { 1, 2, 3 }" & vbCrLf & _
                            "For ctr As Integer = values.GetLowerBound(1) To values.GetUpperBound(1)" & vbCrLf & _
                            "   Console.Write(values(ctr))" & vbCrLf & _
                            "   If ctr < values.GetUpperBound(1) Then Console.Write("", "")" & vbCrLf & _
                            "Next" & vbCrLf & _
                            "Console.WriteLine()"   
      Dim pattern As String = "Console\.Write(Line)?"
      Dim matches As MatchCollection = Regex.Matches(input, pattern)
      For Each match As Match In matches
         Console.WriteLine("'{0}' found in the source code at position {1}.", _ 
                           match.Value, match.Index)       
      Next                            
   End Sub
End Module
' The example displays the following output:
'    'Console.Write' found in the source code at position 115.
'    'Console.Write' found in the source code at position 184.
'    'Console.WriteLine' found in the source code at position 211.

Example 2

The following example calls the Match(String, String) and NextMatch methods to retrieve one match at a time.

using System;
using System.Text.RegularExpressions;

public class Example
{
   public static void Main()
   {
      string input = "int[] values = { 1, 2, 3 };\n" +
                     "for (int ctr = values.GetLowerBound(1); ctr <= values.GetUpperBound(1); ctr++)\n" +
                     "{\n" +
                     "   Console.Write(values[ctr]);\n" +
                     "   if (ctr < values.GetUpperBound(1))\n" +
                     "      Console.Write(\", \");\n" +
                     "}\n" +
                     "Console.WriteLine();\n";   
      string pattern = @"Console\.Write(Line)?";
      Match match = Regex.Match(input, pattern);
      while (match.Success)
      {
         Console.WriteLine("'{0}' found in the source code at position {1}.",  
                           match.Value, match.Index);
         match = match.NextMatch();
      }
   }
}
// The example displays the following output:
//    'Console.Write' found in the source code at position 112.
//    'Console.Write' found in the source code at position 184.
//    'Console.WriteLine' found in the source code at position 207.

Imports System.Text.RegularExpressions

Module Example
   Public Sub Main()
      Dim input As String = "Dim values() As Integer = { 1, 2, 3 }" & vbCrLf & _
                            "For ctr As Integer = values.GetLowerBound(1) To values.GetUpperBound(1)" & vbCrLf & _
                            "   Console.Write(values(ctr))" & vbCrLf & _
                            "   If ctr < values.GetUpperBound(1) Then Console.Write("", "")" & vbCrLf & _
                            "Next" & vbCrLf & _
                            "Console.WriteLine()"   
      Dim pattern As String = "Console\.Write(Line)?"
      Dim match As Match = Regex.Match(input, pattern)
      Do While match.Success
         Console.WriteLine("'{0}' found in the source code at position {1}.", _ 
                           match.Value, match.Index)
         match = match.NextMatch()                  
      Loop                            
   End Sub
End Module
' The example displays the following output:
'    'Console.Write' found in the source code at position 115.
'    'Console.Write' found in the source code at position 184.
'    'Console.WriteLine' found in the source code at position 211.

Remarks

The Match object is immutable and has no public constructor. An instance of the Match class is returned by the Regex.Match method and represents the first pattern match in a string. Subsequent matches are represented by Match objects returned by the Match.NextMatch method. In addition, a MatchCollection object that consists of zero, one, or more Match objects is returned by the Regex.Matches method.

If the Regex.Matches method fails to match a regular expression pattern in an input string, it returns an empty MatchCollection object. You can then use a foreach construct in C# or a For Each construct in Visual Basic to iterate the collection.

If the Regex.Match method fails to match the regular expression pattern, it returns a Match object that is equal to Match.Empty. You can use the Success property to determine whether the match was successful. The following example provides an illustration.

// Search for a pattern that is not found in the input string.
string pattern = "dog";
string input = "The cat saw the other cats playing in the back yard.";
Match match = Regex.Match(input, pattern);
if (match.Success )
   // Report position as a one-based integer.
   Console.WriteLine("'{0}' was found at position {1} in '{2}'.", 
                     match.Value, match.Index + 1, input);
else
   Console.WriteLine("The pattern '{0}' was not found in '{1}'.",
                     pattern, input);

' Search for a pattern that is not found in the input string.
Dim pattern As String = "dog"
Dim input As String = "The cat saw the other cats playing in the back yard."
Dim match As Match = Regex.Match(input, pattern)
If match.Success Then
   ' Report position as a one-based integer.
   Console.WriteLine("'{0}' was found at position {1} in '{2}'.", _ 
                     match.Value, match.Index + 1, input)
Else
   Console.WriteLine("The pattern '{0}' was not found in '{1}'.", _
                     pattern, input)
End If

If a pattern match is successful, the Value property contains the matched substring, the Index property indicates the zero-based starting position of the matched substring in the input string, and the Length property indicates the length of matched substring in the input string.

Because a single match can involve multiple capturing groups, Match has a Groups property that returns the GroupCollection. The Match instance itself is equivalent to the first object in the collection, at Match.Groups[0] (Match.Groups(0) in Visual Basic), which represents the entire match. You can access the captured groups in a match in the following ways:

• You can iterate the members of the GroupCollection object by using a foreach (C#) or For Each (Visual Basic) construct.

• You can use the GroupCollection.Item[Int32] property to retrieve groups by the number of the capturing group. Note that you can determine which numbered groups are present in a regular expression by calling the instance Regex.GetGroupNumbers method.

• You can use the GroupCollection.Item[String] property to retrieve groups by the name of the capturing group. Note that you can determine which named groups are present in a regular expression by calling the instance Regex.GetGroupNames() method.

Properties

Captures	Gets a collection of all the captures matched by the capturing group, in innermost-leftmost-first order (or innermost-rightmost-first order if the regular expression is modified with the RightToLeft option). The collection may have zero or more items. (Inherited from Group)
Empty	Gets the empty group. All failed matches return this empty match.
Groups	Gets a collection of groups matched by the regular expression.
Index	The position in the original string where the first character of the captured substring is found. (Inherited from Capture)
Length	Gets the length of the captured substring. (Inherited from Capture)
Name	Returns the name of the capturing group represented by the current instance. (Inherited from Group)
Success	Gets a value indicating whether the match is successful. (Inherited from Group)
Value	Gets the captured substring from the input string. (Inherited from Capture)
ValueSpan	Gets the captured span from the input string. (Inherited from Capture)

Methods

Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
NextMatch()	Returns a new Match object with the results for the next match, starting at the position at which the last match ended (at the character after the last matched character).
Result(String)	Returns the expansion of the specified replacement pattern.
Synchronized(Match)	Returns a Match instance equivalent to the one supplied that is suitable to share between multiple threads.
ToString()	Retrieves the captured substring from the input string by calling the Value property. (Inherited from Capture)

See also

• MatchCollection
• Regex