程序代码：

OleDbConnection aConnection = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Application.StartupPath + "/" + "DB.mdb");
             aConnection.Open();///打开数据库
             String SQLString = "select * from user where name='" + textBox1.Text + "' and password='" + textBox2.Text + "' ";///设置sql 查询语句
             OleDbDataAdapter myadapter = new OleDbDataAdapter(SQLString, aConnection); ///创建适配器，执行sql 查询
             DataSet ds = new DataSet(); ///建立数据集
             myadapter.Fill(ds); ///将查询结果加入 ds 中
             if (ds.Tables[0].Rows.Count > 0)
             {
                  OleDbDataAdapter qx_adapter = new OleDbDataAdapter("select qx from user where name='" + textBox1.Text.Trim() + "'", aConnection);
                  DataSet ds_qx = new DataSet();
                  qx_adapter.Fill(ds_qx);
                  qx = Convert.ToInt32(ds_qx.Tables[0].Rows[0]["qx"]);
                    /// textBox4.Text = Convert.ToString(qx);
                  form2_01.Show();
                  form2_01.cdxs(qx);
             }
             else
             {
                 MessageBox.Show("你按了确定");
                 MessageBox.Show("对不起，请输入正确的用户名和密码");
             }
             aConnection.Close();///关闭数据库连接（必须）
             this.Hide();