The Regex.Split(string) methods are similar to the string.Split(Char[]) method, except that Regex.Split(string) splits the string at a delimiter determined by a regular expression instead of a set of characters. The string is split as many times as possible. If no delimiter is found, the return value contains one element whose value is the original input string.

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 Elements.

If multiple matches are adjacent to one another, an empty string is inserted into the array. For example, splitting a string on a single hyphen causes the returned array to include an empty string in the position where two adjacent hyphens are found.

If a match is found at the beginning or the end of the input string, an empty string is included at the beginning or the end of the returned array. The following example uses the regular expression pattern [a-z]+ to split an input string on any uppercase or lowercase alphabetic character. Because the string begins and ends with matching alphabetic characters, the value of the first and last element of the returned array is string.Empty.

code reference: System.Text.RegularExpressions.Regex.Split#23

If capturing parentheses are used in a Regex.Split(string) expression, any captured text is included in the resulting string array. For example, if you split the string "plum-pear" on a hyphen placed within capturing parentheses, the returned array includes a string element that contains the hyphen.

code reference: System.Text.RegularExpressions.Regex.Split#9

However, when the regular expression pattern includes multiple sets of capturing parentheses, the behavior of this method depends on the version of the .NET Framework. In the .NET Framework 1.0 and 1.1, if a match is not found within the first set of capturing parentheses, captured text from additional capturing parentheses is not included in the returned array. Starting with the .NET Framework 2.0, all captured text is also added to the returned array. For example, the following code uses two sets of capturing parentheses to extract the elements of a date, including the date delimiters, from a date string. The first set of capturing parentheses captures the hyphen, and the second set captures the forward slash. If the example code is compiled and run under the .NET Framework 1.0 or 1.1, it excludes the slash characters; if it is compiled and run under the .NET Framework 2.0 or later versions, it includes them.

code reference: System.Text.RegularExpressions.Regex.Split#10

If the regular expression can match the empty string, Regex.Split(string) will split the string into an array of single-character strings because the empty string delimiter can be found at every location.

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. If no match is found in that time interval, the method throws a System.Text.RegularExpressions.RegexMatchTimeoutException exception. matchTimeout overrides any default time-out value defined for the application domain in which the method executes.

Namespace: System.Text.RegularExpressions
Assembly: System (in System.dll)
Assembly Versions: 4.0.0.0