Extension Method，以string為例

Extension Method，寫ASP.NET MVC會常用來擴充HTML Helper
DEMO
https://dotnetfiddle.net/c7QUTG


深入探討 C# 之 Extension Method
https://oomusou.io/csharp/extension-method/

ASP.NET MVC 你一定要知道怎麼創立HTML Helper
http://demo.tc/post/459