protected void btnDel_Click(object sender, EventArgs e)
{
DALstudent_course dal = new DALstudent_course();
student_courseEntity course = new student_courseEntity();
dal.Delstudent_course(int.Parse(lbx2.SelectedValue));
Response.Write("<script>alert('放弃成功');location.href='CourseSelect.aspx'</script>");
}
