Using Regular Expressions

Regular expressions are a systematic way of searching, replacing, and parsing text with elaborate patterns of characters. The System.Text.RegularExpressions namespace provides an avenue to the .NET Framework’s regular expression engine. The Regex class is used to compile regular expressions.

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Common Methods (Full List)

• IsMatch – Indicates whether the regular expression finds a match in the input string.
• Match – Searches an input string for an occurrence of a regular expression and returns the precise result.
• Matches – Searches an input string for all occurrences of a regular expression and returns all the successful matches.
• Replace – Within a specified input string, replaces strings that match a regular expression pattern with a specified replacement string.
• Split – Splits an input string into an array of substrings at the positions defined by a regular expression match.

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The Code

Regular Expressions – C# Code Sample

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The Result

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Regular Expressions can be very complex and there may be several ways to “skin a cat” so to speak. After spending just a couple of minutes surfing the net I found three different patterns for phone numbers.  

^[2-9]\d{2}-\d{3}-\d{4}$ –> 800-555-5555
^(\d{3}-\d{3}-\d{4})*$ –> 555-555-1212
^(\([2-9]|[2-9])(\d{2}|\d{2}\))(-|.|\s)?\d{3}(-|.|\s)?\d{4}$ –> 213-123-1234, 2131231234, (213) 123-1234

There are websites and tools dedicated to the creation of Regular Expressions.  For instance, Roy Osherove is the creator of a tool called Regulazy.  Regulazy is a visual Regex creation tool for beginners.  There are so many different expression patterns, it is easy to see why there is a need for tools such as this.

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More Information

• Regular Expressions Library
• Regular Expressions Information
• Regular Expressions Cheat Sheet

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