Regex.Match Method (String, String, RegexOptions, TimeSpan)
Searches the input string for the first occurrence of the specified regular expression, using the specified matching options and time-out interval.
Assembly: System (in System.dll)
public static Match Match( string input, string pattern, RegexOptions options, TimeSpan matchTimeout )
- Type: System.String
The string to search for a match.
- Type: System.String
The regular expression pattern to match.
- Type: System.Text.RegularExpressions.RegexOptions
A bitwise combination of the enumeration values that provide options for matching.
Return ValueType: System.Text.RegularExpressions.Match
An object that contains information about the match.
A regular expression parsing error occurred.
input or pattern is null.
options is not a valid bitwise combination of RegexOptions values.
matchTimeout is negative, zero, or greater than approximately 24 days.
A time-out occurred. For more information about time-outs, see the Remarks section.
The method returns the first substring that matches a regular expression pattern in an input string. For information about the language elements used to build a regular expression pattern, see Regular Expression Language - Quick Reference.
The pattern parameter consists of regular expression language elements that symbolically describe the string to match. For more information about regular expressions, see .NET Framework Regular Expressions and Regular Expression Language - Quick Reference.
You can determine whether the regular expression pattern has been found in the input string by checking the value of the returned Match object's Success property. If a match is found, the returned Match object's Value property contains the substring from input that matches the regular expression pattern. If no match is found, its value is String.Empty.
This method returns the first substring found in input that matches the regular expression pattern. You can retrieve subsequent matches by repeatedly calling the returned Match object's NextMatch method. You can also retrieve all matches in a single method call by calling the Regex.Matches(String, String, RegexOptions) method.
The matchTimeout parameter specifies how long a pattern matching method should try to find a match before it times out. Setting a time-out interval prevents regular expressions that rely on excessive backtracking from appearing to stop responding when they process input that contains near matches. For more information, see Best Practices for Regular Expressions in the .NET Framework and Backtracking in Regular Expressions. If no match is found in that time interval, the method throws a RegexMatchTimeoutException exception. matchTimeout overrides any default time-out value defined for the application domain in which the method executes.Notes to Callers
We recommend that you set the matchTimeout parameter to an appropriate value, such as two seconds. If you disable time-outs by specifying Regex.InfiniteMatchTimeout, the regular expression engine offers slightly better performance. However, you should disable time-outs only under the following conditions:
When the input processed by a regular expression is derived from a known and trusted source or consists of static text. This excludes text that has been dynamically input by users.
When the regular expression pattern has been thoroughly tested to ensure that it efficiently handles matches, non-matches, and near matches.
When the regular expression pattern contains no language elements that are known to cause excessive backtracking when processing a near match.