odp.net 读写oracle blob字段

DEVELOPER: ODP.NET Serving Winning LOBs：

http://www.oracle.com/technetwork/issue-archive/2005/05-nov/o65odpnet-085139.html

Data Provider for .NET Developer's Guide：

https://docs.oracle.com/database/121/ODPNT/OracleBlobClass.htm#ODPNT4035

从blob字段读取一个图片文件的代码：

        OracleConnection con = new OracleConnection(connStr);
         con.Open();

         // statement to get a blob
         string sql = "select yz from sysusers where yhdh='123'";

         // create command object
         // InitialLOBFetchSize
         //  defaults to 0
         OracleCommand cmd = new OracleCommand(sql, con);

         // create a datareader
         using (OracleDataReader dr = cmd.ExecuteReader())
         {
             // read the single row result
             dr.Read();
             // use typed accessor to retrieve the blob
             OracleBlob blob = dr.GetOracleBlob();

             // create a memory stream from the blob
             using (MemoryStream ms = new MemoryStream(blob.Value))
             {
                 // set the image property equal to a bitmap
                 // created from the memory stream
                 pictureBox1.Image = new Bitmap(ms);
             }
         }

保存文件到blob字段的代码：

         con.Open();

         // 利用事务处理（必须）
         OracleTransaction transaction = con.BeginTransaction();
         string sql="select yz from sysusers where yhdh='123' FOR UPDATE";
         OracleCommand cmd = new OracleCommand(sql, con);

         using ( OracleDataReader reader = cmd.ExecuteReader())
         {
             //Obtain the first row of data.
             reader.Read();
             //Obtain a LOB.
             OracleBlob blob = reader.GetOracleBlob();
             blob.Erase();
             // 将文件写入 BLOB 中
             byte[] Buffer;
             FileStream fs = new FileStream(@"d:\01.jpg", FileMode.Open);
             using (MemoryStream ms = new MemoryStream())
             {
                 int b;
                 while ((b = fs.ReadByte()) != -)
                 {
                     ms.WriteByte((byte)b);
                 }
                 Buffer = ms.ToArray();
             }

             // Begin ChunkWrite to improve performance
             // Index updates occur only once after EndChunkWrite
             blob.Position=;
             blob.BeginChunkWrite();  //启用BeginChunkWrite不是必须，只与性能有关
             blob.Write(Buffer, ,Buffer .Length);  //从字节数据写入blob字段
             blob.EndChunkWrite();
             blob.Close();
         }
         // 提交事务
         transaction.Commit();
         con.Close();