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.NET interview questions: - What is time out support in regex (regular expression)?

Some of the regular expressions are very complex and they can take lot of time to evaluate.
For instance below is a simple regular expression.

var regEx = new Regex(@"^(\d+)+$", RegexOptions.Singleline);

If someone inputs a huge number as shown in the below code snippet. It will take more than a minute to resolve the expression leading to lot of load on the application. So we would like to give a time out on the expression. So if the validation takes more than a specific interval we would like the application to give up and move ahead.

var match = regEx.Match("123453109839109283090492309480329489812093809x");

In .NET 4.5 we can now provide the timeout value as parameter on the constructor. For instance in the below code we have provided 2 seconds timeout on the regex (regular expression). So if it exceeds more than 2 second “regexMatchTimeOutException” will occur.



var regEx = new Regex(@"^(\d+)+$", RegexOptions.Singleline, TimeSpan.FromSeconds(2));

var match = regEx.Match("123453109839109283090492309480329489812093809x");



catch (RegexMatchTimeoutException ex)


 Console.WriteLine("Regex Timeout");

Also see following .NET interview questions video on regular expressions & can we see some practical demonstrations: -

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Shivprasad koirala Koirala
I am a Microsoft MVP for ASP/ASP.NET and currently a CEO of a small E-learning company in India. We are very much active in making training videos , writing books and corporate trainings. Do visit my site for .NET, C# , design pattern , WCF , Silverlight , LINQ , ASP.NET , ADO.NET , Sharepoint , UML , SQL Server training and Interview questions and answers
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