Validating an email address with a regular expression

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Below is a quick and dirty post on how to use the C# regular expression library to validate an email address. The regular expression stuff is located in the System.Text.RegularExpression namespace.

So somewhere in my class I use the code below. Now you don't have to do class member variables. You could just do all this code in a function. I however will be doing multiple validations so I don't want to be destroying/creating multiple objects during the life of my class. You have to create your regular expression and then use that expression when creating the RegEx object.

private string _expression = @"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}" +
                             @"\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\" + 
                             @".)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$";

private Regex _validEmailRegEx = new RegEx( _expression );


Then in my class I define a function that uses the RegEx object to validate an email address being passed in. If it passes the reg ex we get true, else we get false.


private bool ValidateEmailAddress( string emailAddress )
{
     return _validEmailRegEx.IsMatch(emailAddress) ? true: false;
}

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