这是原代码   
    private void button3_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();
               string strCom = "DELETE From book where 编号 =";
                strCom +=(string)myDataSet.Tables[0].Rows[a][0];
                Console.WriteLine();
               OleDbCommand delst=new OleDbCommand(strCom,myConn);
               delst.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");}

        }

  

DataSet myDataSet = new DataSet();
string strCom = "DELETE From book where 编号 =";
strCom +=(string)myDataSet.Tables[0].Rows[a][0]

上边刚定义一个myDataSet，这个时候他应该是空的。

myDataSet.Tables[0].Rows[a][0]这句怎么可能正确呢？