using System;
using System.Data;
using System.Text;
using Oracle.DataAccess.Client;
using Oracle.DataAccess.Types;

namespace Sample77
{
    // 演示通过结果集的锁顶来更新 LOB 数据
    class Program
    {
        static void Main(string[] args)
        {
            // Connect
            string constr = "User Id=scott;Password=tiger;Data Source=(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.24)(PORT = 1521))(CONNECT_DATA = (SERVER = DEDICATED)(SERVICE_NAME = bjoracle.oracle10g.mynet)))";
            OracleConnection conn = Connect(constr);

            if (conn == null)
                return;

            // Setup
            Setup(conn);

            // BeginTransaction
            OracleTransaction txn = conn.BeginTransaction();
            OracleCommand cmd = new OracleCommand("", conn);

            try
            {
                // Lock the result set using FOR UPDATE clause
                cmd.CommandText = "select story from multimedia_tab for update";

                OracleDataReader reader = cmd.ExecuteReader();
                reader.Read();
                OracleClob clob = reader.GetOracleClob(0);
                Console.WriteLine("Old Data: {0}", clob.Value);

                // Modify the clob column of the row
                string ending = " The end.";
                clob.Append(ending.ToCharArray(), 0, ending.Length);

                // Release the lock
                txn.Commit();

                // Fetch the new data; transaction or locking not required.
                cmd.CommandText = "select story from multimedia_tab";
                reader = cmd.ExecuteReader();
                while (reader.Read())
                {
                    clob = reader.GetOracleClob(0);
                    Console.WriteLine("New Data: {0}", clob.Value);
                }
                
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error: {0}", ex.Message);
            }
            finally
            {
                // Dispose OracleCommand object
                cmd.Dispose();

                // Close and Dispose OracleConnection object
                conn.Close();
                conn.Dispose();
            }

            // Waiting
            Console.ReadLine();
        }

        // Opening a new Connection
        public static OracleConnection Connect(string connectStr)
        {
            OracleConnection conn = new OracleConnection(connectStr);
            try
            {
                conn.Open();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error: {0}", ex.Message);
                conn = null;
            }
            return conn;
        }

        // Setup the necessary Tables & Test Data
        public static void Setup(OracleConnection conn)
        {
            StringBuilder blr;
            OracleCommand cmd = new OracleCommand("", conn);

            blr = new StringBuilder();
            blr.Append("DROP TABLE multimedia_tab");
            cmd.CommandText = blr.ToString();
            try
            {
                cmd.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Warning: {0}", ex.Message);
            }

            blr = new StringBuilder();
            blr.Append("CREATE TABLE multimedia_tab(thekey NUMBER(4) PRIMARY KEY,");
            blr.Append("story CLOB, sound BLOB)");
            cmd.CommandText = blr.ToString();
            try
            {
                cmd.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error: {0}", ex.Message);
            }

            blr = new StringBuilder();
            blr.Append("INSERT INTO multimedia_tab values(");
            blr.Append("1,");
            blr.Append("'This is a long story.Once upon a time',");
            blr.Append("'898787787874454654564578978971114544897')");
            cmd.CommandText = blr.ToString();

            try
            {
                cmd.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error: {0}", ex.Message);
            }

            blr = new StringBuilder();
            blr.Append("INSERT INTO multimedia_tab values(");
            blr.Append("2,");
            blr.Append("'This is the second long story.Once upon a time',");
            blr.Append("'898787787874454654564578978971114544897')");
            cmd.CommandText = blr.ToString();

            try
            {
                cmd.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error: {0}", ex.Message);
            }
        }
    }
}