C# 读写 Oracle BLOB 数据

using System;
using System.Data.OracleClient;
using System.IO;

namespace fenghua.Data.Oracle
{
///
/// Class1 的摘要说明。
///
public class OracleLobData
{
private OracleConnection conn;
public OracleLobData()
{
//
// TODO: 在此处添加构造函数逻辑
//
}

/*
* 在调用此函数之前需要写插入一个字符串到 BLOB 中比如：
* Select some data.
* Table Schema:
* "CREATE TABLE tablewithlobs (a int, b BLOB, c CLOB, d NCLOB)";
* "INSERT INTO tablewithlobs values (1, 'AA', 'AAA', N'AAAA')";
* 否则程序会在 OracleLob tempLob = reader.GetOracleLob(0) 处出错。
*/
///
/// 文件写入到 Oracle Blob 字段中。
///
///
id 值
///
文件名
///
id 键
///
blob 键
///
表名
public void WriteBlob(int idData, string fileName, string id, string blob, string tableName)
{
string connString = "server=oratest;User ID=kttest;Password=test";
using(conn = new OracleConnection(connString))
{
try
{
conn.Open();
OracleCommand cmd = conn.CreateCommand();

// 利用事务处理（必须）
OracleTransaction transaction = cmd.Connection.BeginTransaction();
cmd.Transaction = transaction;

// 获得 OracleLob 指针
cmd.CommandText = "select " + blob + " from " + tableName + " where " + id + " = " + idData + " FOR UPDATE";
OracleDataReader reader = cmd.ExecuteReader();
using(reader)
{
//Obtain the first row of data.
reader.Read();
//Obtain a LOB.
OracleLob tempLob = reader.GetOracleLob(0);

// 将文件写入 BLOB 中
FileStream fs = new FileStream(fileName,FileMode.Open);
tempLob.BeginBatch(OracleLobOpenMode.ReadWrite);
int length = 10485760;
byte[] Buffer = new byte[length];
int i;
while((i = fs.Read(Buffer,0,length)) > 0)
{
tempLob.Write(Buffer,0,i);
}
fs.Close();
tempLob.EndBatch();
cmd.Parameters.Clear();
}
// 提交事务
transaction.Commit();
}
catch(Exception ex)
{
throw ex;
}
finally
{
conn.Close();
}
}
}

///
/// 读取 Oracle Blob 到文件中。
///
///
id 值
///
文件名
///
id 键
///
blob 键
///
表名
public void ReadBlob(int idData,string fileName, string id, string blob, string tableName)
{
string connString = "server=oratest;User ID=kttest;Password=test";
using(conn = new OracleConnection(connString))
{
try
{
conn.Open();
OracleCommand cmd = conn.CreateCommand();

// 利用事务处理（必须）
OracleTransaction transaction = cmd.Connection.BeginTransaction();
cmd.Transaction = transaction;

// 获得 OracleLob 指针
string sql = "select " + blob + " from " + tableName + " where " + id + " = " + idData;
cmd.CommandText = sql;
OracleDataReader dr = cmd.ExecuteReader();
dr.Read();
OracleLob tempLob = dr.GetOracleLob(0);
dr.Close();

// 读取 BLOB 中数据，写入到文件中
FileStream fs = new FileStream(fileName,FileMode.Create);
int length = 1048576;
byte[] Buffer = new byte[length];
int i;
while((i = tempLob.Read(Buffer,0,length)) > 0)
{
fs.Write(Buffer,0,i);
}
fs.Close();
tempLob.Clone();
cmd.Parameters.Clear();

// 提交事务
transaction.Commit();
}
catch(Exception ex)
{
throw ex;
}
finally
{
conn.Close();
}
}
}
}
}