//tabControl的选项卡改变时发生（即为选择的专业改变了）
private void tbClassInfo_Selecting(object sender, TabControlCancelEventArgs e)
{
int speciality_id = (int)e.TabPage.Tag; //获取当前选中“专业”page的Id;
CourseBLL bll_course = new CourseBLL();
List <Course> list = bll_course.GetCoursesBySpecialityId(speciality_id);
//绑定数据
DataGridView dgvCourse = e.TabPage.Controls["dgvCourse"] as DataGridView;
dgvCourse.DataSource = list;
}