有时候图省事，属性这样写public int pageCount{get{return pageCount;}set{pageCount=value;}}可能会报栈溢出的错误，
StackOverflowException: The requested operation caused a stack overflow.
需要保存值时还是要写到字段里，属性无法保存，如下写法：
private int pageCount;
public int PageCount{get{return pageCount;}set{pageCount=value;}}
