对oracle中的BLOB的操作(读取，写入)

 将BLOB保存为本地文档：
/// <summary>
/// 读出Blob字段
/// </summary>
/// <param name="commandText">sql语句，执行结果为BLOB数据</param>
/// <param name="DocumentAddress">将要把BLOB数据保存为的文档的路径</param>
public void ReadBlob(string commandText, string DocumentAddress)
{
try
{
Open();
cmd.Connection = conn;
cmd.CommandType = CommandType.Text;
cmd.CommandText = commandText;
// 利用事务处理（必须）
OracleTransaction transaction = cmd.Connection.BeginTransaction();
cmd.Transaction = transaction;
reader = cmd.ExecuteReader();
reader.Read();
OracleLob BLOB = reader.GetOracleLob(0);
reader.Close();
FileStream DataStream = new FileStream(DocumentAddress, FileMode.Create);
int length = 30485760;
byte[] Buffer = new byte[length];
int i;
while ((i = BLOB.Read(Buffer, 0, length)) > 0)
{
DataStream.Write(Buffer, 0, i);
}
DataStream.Close();
BLOB.Clone();
cmd.Transaction.Commit();
}
catch (OracleException e)
{
cmd.Transaction.Rollback();
throw e;
}
finally
{
Close();
}
}

将本地文档保存为BLOB类型：
/// <summary>
/// 写入Blob字段
/// </summary>
/// <param name="commandText">sql语句，执行结果为BLOB数据</param>
/// <param name="DocumentAddress">本地文档的路径</param>
public void WriteBlob(string commandText, string DocumentAddress