MatchCollection Class

MatchCollection Class


Represents the set of successful matches found by iteratively applying a regular expression pattern to the input string.

Namespace:   System.Text.RegularExpressions
Assembly:  System (in System.dll)


public class MatchCollection : ICollection, IEnumerable


Gets the number of matches.


Gets a value that indicates whether the collection is read only.


Gets a value indicating whether access to the collection is synchronized (thread-safe).


Gets an individual member of the collection.


Gets an object that can be used to synchronize access to the collection.

System_CAPS_pubmethodCopyTo(Array, Int32)

Copies all the elements of the collection to the given array starting at the given index.


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)


Provides an enumerator that iterates through the collection.


Serves as the default hash function. (Inherited from Object.)


Gets the Type of the current instance.(Inherited from Object.)


Creates a shallow copy of the current Object.(Inherited from Object.)


Returns a string that represents the current object.(Inherited from Object.)


Overloaded. Enables parallelization of a query.(Defined by ParallelEnumerable.)


Overloaded. Converts an IEnumerable to an IQueryable.(Defined by Queryable.)


Casts the elements of an IEnumerable to the specified type.(Defined by Enumerable.)


Filters the elements of an IEnumerable based on a specified type.(Defined by Enumerable.)

The collection is immutable (read-only) and has no public constructor. The Regex.Matches method returns a MatchCollection object.

The collection contains zero or more System.Text.RegularExpressions.Match objects. If the match is successful, the collection is populated with one System.Text.RegularExpressions.Match object for each match found in the input string. If the match is unsuccessful, the collection contains no System.Text.RegularExpressions.Match objects, and its Count property equals zero.

When applying a regular expression pattern to a particular input string, the regular expression engine uses either of two techniques to build the MatchCollection object:

  • Direct evaluation.

    The MatchCollection object is populated all at once, with all matches resulting from a particular call to the Regex.Matches method. This technique is used when the collection's Count property is accessed. It typically is the more expensive method of populating the collection and entails a greater performance hit.

  • Lazy evaluation.

    The MatchCollection object is populated as needed on a match-by-match basis. It is equivalent to the regular expression engine calling the Regex.Match method repeatedly and adding each match to the collection. This technique is used when the collection is accessed through its GetEnumerator method, or when it is accessed using the foreach statement (in C#) or the For Each...Next statement (in Visual Basic).

To iterate through the members of the collection, you should use the collection iteration construct provided by your language (such as foreach in C# and For EachNext in Visual Basic) instead of retrieving the enumerator that is returned by the GetEnumerator method.

The following example illustrates the use of the MatchCollection class to interrogate a set of Match instances.

using System;
using System.Text.RegularExpressions;

public class Test

    public static void Main ()

        // Define a regular expression for repeated words.
        Regex rx = new Regex(@"\b(?<word>\w+)\s+(\k<word>)\b",
          RegexOptions.Compiled | RegexOptions.IgnoreCase);

        // Define a test string.        
        string text = "The the quick brown fox  fox jumped over the lazy dog dog.";

        // Find matches.
        MatchCollection matches = rx.Matches(text);

        // Report the number of matches found.
        Console.WriteLine("{0} matches found in:\n   {1}", 

        // Report on each match.
        foreach (Match match in matches)
            GroupCollection groups = match.Groups;
            Console.WriteLine("'{0}' repeated at positions {1} and {2}",  


// The example produces the following output to the console:
//       3 matches found in:
//          The the quick brown fox  fox jumped over the lazy dog dog.
//       'The' repeated at positions 0 and 4
//       'fox' repeated at positions 20 and 25
//       'dog' repeated at positions 50 and 54

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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