Understand office model

http://www.microsoft.com/china/msdn/library/office/office/UndstaExcelObjModNETDev.mspx

1. 使用VBA(visual basic for applications)开发比使用C#开发方便
2. Application提供对整个应用程序的封装；Workbook为Worksheet collections；Range对应Cell or Cells;
3. Many Excel methods/functions return object type or depend upon dynamic bind. For example:Application.ActiveSheet returns not Worksheet but object;