private void button4_Click(object sender, EventArgs e)
        {
            try
            {
                int a = this.dataGrid1.CurrentCell.RowNumber;
                string strCon = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\\c#\\book.mdb";
                OleDbConnection myConn = new OleDbConnection(strCon);
                myConn.Open();
                DataSet myDataSet = new DataSet();
                OleDbCommand command = new OleDbCommand("SELECT * FROM book order by 编号 ", myConn);
                OleDbDataAdapter ads = new OleDbDataAdapter(command);
                ads.Fill(myDataSet);
                string strCom = "UPDATE book set 书名='" + myDataSet.Tables["book"].Rows[a][1] + "',作者='" + myDataSet.Tables["book"].Rows[a][2] + "',价格=" + myDataSet.Tables["book"].Rows[a][3] + ",书架号=" + myDataSet.Tables["book"].Rows[a][4] + " where 编号=" + myDataSet.Tables["book"].Rows[a][0] +"";
                OleDbCommand inst = new OleDbCommand(strCom, myConn);
                inst.ExecuteNonQuery();
                OleDbDataAdapter myCommand = new OleDbDataAdapter("SELECT *FROM book order by 编号", myConn);
                myDataSet.Clear();
                myCommand.Fill(myDataSet, "book");
                this.dataGrid1.DataSource = myDataSet.Tables["book"];
                myConn.Close();
            }
            catch (Exception x)
            {
                MessageBox.Show("错误" + x.ToString(), "error" );
            }
        }