System.Text.RegularExpressions.Regex regex应该是regular expression的缩写
https://msdn.microsoft.com/zh-cn/library/system.text.regularexpressions.regex(v=vs.110).aspx
Represents an immutable regular expression.【immutable 不可变的】 代表了不可变的正则表达式
The Regex class represents the .NET Framework‘s regular expression engine. It can be used to quickly parse large amounts of text to find specific character patterns; to extract, edit, replace, or delete text substrings; and to add the extracted strings to a collection to generate a report.
System.Configuration.RegexStringValidator
Provides validation of a string based on the rules provided by a regular expression.
C#中【正则表达式regular expression】相关的知识
原文：http://www.cnblogs.com/chucklu/p/4252864.html