csharp: Oracle Metadata queries

    /// <summary>
    /// 对于本文的Oracle安装来说，data source对应着Oracle_Client\oracle\ora92\network\admin\tnsnames.ora配置文件中的网络服务名
    /// Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = geovin)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = geovindu)));user id=sysdba;password=0214;Persist Security Info=True;";
    /// 涂聚文 20150516
    /// </summary>
    public partial class Form1 : Form
    {
        public string connectionString = @"Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = geovistu-xwvuyh)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = oracle9i)));user id=geovin;password=0214;Persist Security Info=True;";
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        DataTable setDatat()
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("id", typeof(int));
            dt.Columns.Add("name", typeof(string));
            dt.Rows.Add(1, "Procedures");
            dt.Rows.Add(2, "DataTypes");
            dt.Rows.Add(3, "Foreign Keys");
            dt.Rows.Add(4, "Databases");
            dt.Rows.Add(5, "dbo");
            dt.Rows.Add(6, "Arguments");
            dt.Rows.Add(7, "Collection Name");
            dt.Rows.Add(8, "DatasourceInformation");
            dt.Rows.Add(9, "MetaDataCollections");
            dt.Rows.Add(10, "ForeignKeyColumns");
            dt.Rows.Add(11, "Functions");
            dt.Rows.Add(12, "IndexColumns");
            dt.Rows.Add(13, "Indexes");
            dt.Rows.Add(14, "PrimaryKeys");
            dt.Rows.Add(15, "ReservedWords");
            dt.Rows.Add(16, "Restrictions");
            dt.Rows.Add(17, "Triggers");
            dt.Rows.Add(18, "UDFs");
            dt.Rows.Add(19, "UniqueKeys");
            dt.Rows.Add(20, "UserPrivileges");
            dt.Rows.Add(21, "Users");
            dt.Rows.Add(22, "ViewColumns");

            //DataTable dt = connection.GetSchema("Tables", strRestricted);
            dt.Rows.Add(23, "Tables");
            dt.Rows.Add(24, "Columns");//表的列的详细，有主键TABLE_CATALOG,TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,ORDINAL_POSITION,COLUMN_DEFAULT,IS_NULLABLE,DATA_TYPE,CHARACTER_MAXIMUM_LENGTH,NUMERIC_PRECISION,NUMERIC_SCALE,DATETIME_PRECISION,CHARACTER_SET_NAME,COLLATION_NAME,COLUMN_TYPE,COLUMN_KEY,EXTRA,PRIVILEGES,COLUMN_COMMENT
            dt.Rows.Add(25, "Views");
            dt.Rows.Add(26, "Indexes");//表的列
            dt.Rows.Add(27, "IndexColumns");//主键

            return dt;
        }
        /// <summary>
        /// 
        /// </summary>
        public Form1()
        {
            InitializeComponent();
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Form1_Load(object sender, EventArgs e)
        {
            this.txtConnection.Text = connectionString;
            this.comboBox1.DataSource = setDatat();
            this.comboBox1.DisplayMember = "name";
            this.comboBox1.ValueMember = "id";
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                using (OracleConnection connection = new OracleConnection(connectionString))
                {
                    connection.Open();
                    //MessageBox.Show(connection.State.ToString());
                    DataTable dt = connection.GetSchema(this.comboBox1.Text.Trim());
                    this.dataGridView1.DataSource = dt;
                    this.textBox1.Text = GetColumnNames(dt);

                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
                ex.Message.ToString();
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button2_Click(object sender, EventArgs e)
        {
            string connString = "Provider=OraOLEDB.Oracle.1;User ID=geovin;Password=0214;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = geovistu-xwvuyh)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = oracle9i)))";
            OleDbConnection conn = new OleDbConnection(connString);
            try
            {
                conn.Open();
                //MessageBox.Show(conn.State.ToString());
                DataTable dt = conn.GetSchema(this.comboBox1.Text.Trim());
                this.dataGridView1.DataSource = dt;
                this.textBox1.Text = GetColumnNames(dt);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
            }
            finally
            {
                conn.Close();
            }
        }