What is Regex & How to use Regular Expressions with C#?

Regexes (or Regular Expressions) are a way to process text and perform a variety of pattern matching processes on them.

And example would be to write an application to rename all your MP3 files to have a "MY MUSIC" prefix:

public static Regex regex = new Regex(
      "^(?<!MYMUSIC)(.*\\.MP3)$",
    RegexOptions.IgnoreCase
    | RegexOptions.Multiline
    | RegexOptions.Singleline
    | RegexOptions.IgnorePatternWhitespace
    | RegexOptions.Compiled
    );


// This is the replacement string
public static string regexReplace =
      "MYMUSIC$1";


// Replace the matched text in the InputText using the replacement pattern
 string result = regex.Replace(InputText,regexReplace);