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);

             }

         }

         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();