This property reflects the value of the regexInput parameter of the RegexMatchTimeoutException.#ctor(string, string, TimeSpan) constructor. If this parameter is not explicitly initialized in a constructor call, its value is string.Empty.

When the exception is thrown by the regular expression engine, the value of the RegexMatchTimeoutException.Input property reflects the entire input string passed to the regular expression engine. It does not reflect a partial string, such as the substring that the engine searches in the call to a method such as Regex.Match(string, int).