COM原理比较简单，但在实现时比较灵活，这就造成了大多数人感到难以掌握，其实只要抓住COM的本质，其他的东西都比较简单。-COM principle is relatively simple, but in achieving a more flexible time, which caused the majority of people find it difficult to grasp, if the COM grasp the essence of the other things are relatively simple.