private void btnXoa_Click(object sender, EventArgs e)
        {
            int r = dgvQLSach.CurrentCell.RowIndex;

            int          rSelected = (int)dgvQLSach.Rows[r].Cells[0].Value;
            DialogResult traloi;

            traloi = MessageBox.Show("Ban co muon xoa mau tin nay ko?", "Tra loi"
                                     , MessageBoxButtons.YesNo, MessageBoxIcon.Question);
            if (traloi == DialogResult.Yes)
            {
                db.Configuration.LazyLoadingEnabled = false;
                string Tensach = txtTenSach.Text;
                db.sp_Delete_Book(Tensach);
                //using (var db = new Model1())
                //{
                //    db.Configuration.LazyLoadingEnabled = false;
                //    var query = from d in db.SACHes
                //                where d.MASACH == rSelected
                //                select d;
                //    foreach (var MASACH in query)
                //    {
                //        db.SACHes.Remove(MASACH);
                //    }
                //    db.SaveChanges();
                //}
                db.SaveChanges();
                LoadData();
                MessageBox.Show("Da Xoa Xong!");
            }
            //else
            //{
            //    MessageBox.Show("Ban Da Bam Khong!");
            //}
        }