分页

public int PageCount {
            get {
                if (dataSource == null)
                    return 0;

                int dataSourceItemCount = DataSourceCount;
                if (IsPagingEnabled && (dataSourceItemCount > 0)) {
                    int pageCountNum = dataSourceItemCount + pageSize - 1;
                    if (pageCountNum < 0) {
                        return 1;   // integer overflow
                    }
                    return (int)(pageCountNum/pageSize);
                }
                else {
                    return 1;
                }
            }
        }