This is in reference to: byte[] and efficiently passing by reference
And the SqlDataReader found in this post: Getting binary data using SqlDataReader
Inside a loop, I'm calling a database and returning a large object (varbinary[max]). Currently, I'm running into OutOfMemory exceptions, so I'm trying to reduce the footprint in the Large Object Heap (LOH).
So, I'm creating a byte array for the largest file that I'd download and adding some padding just in case. For instance:
byte[] currentFile = new byte[largestFileSize * 1.1]; I then pass this currentFile the database method. Currently, we use the EnterpriseLibrary to access the database:
DbCommand storedProcedure = MedicareDatabase.Db.GetStoredProcCommand(spName); storedProcedure.CommandTimeout = 5000; if (parameters != null) { foreach (Param parameter in parameters) { if (parameter != null) { MedicareDatabase.Db.AddInParameter(storedProcedure, parameter.ParameterName, parameter.DbType, parameter.Value); } } } try { BinaryWriter bw; // Streams the BLOB to the FileStream object. int bufferSize = 100; // Size of the BLOB buffer. byte[] outbyte = new byte[bufferSize]; // The BLOB byte[] buffer to be filled by GetBytes. long retval; // The bytes returned from GetBytes. long startIndex = 0; // The starting position in the BLOB output. var myReader = MedicareDatabase.Db.ExecuteReader(storedProcedure); while (myReader.Read()) { bw = new BinaryWriter(); // Reset the starting byte for the new BLOB. startIndex = 0; // Read the bytes into outbyte[] and retain the number of bytes returned. retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize); // Continue reading and writing while there are bytes beyond the size of the buffer. while (retval == bufferSize) { bw.Write(outbyte); bw.Flush(); // Reposition the start index to the end of the last buffer and fill the buffer. startIndex += bufferSize; retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize); } // Write the remaining buffer. bw.Write(outbyte, 0, (int)retval - 1); bw.Flush(); // Close the output file. bw.Close(); } This is a modification of the code listed in the second article above.
Here are my questions (and feel free to correct me if I should be asking different questions)
How do you efficiently refill the
byte[]without creating a new object?The above code doesn't use the
CommandBehavior.SequentialAccesswhich is needed to also not create a new object. How do I use theEnterpriseLibrarywithCommandBehaviors?
I'm calling the database and returning have a byte[] array
Updated
So after some time, I've decided to manually populate the byte array. The reference is now being passed successfully.
SqlConnection pubsConn = null; SqlCommand logoCMD = null; SqlDataReader myReader = null; try { pubsConn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["MedicareAccess"].ConnectionString); logoCMD = new SqlCommand("esMD.proc_WS_SelectBiztalkBinary", pubsConn); logoCMD.CommandType = CommandType.StoredProcedure; SqlParameter submissionSetParamter = logoCMD.Parameters.Add("@submissionSetId", SqlDbType.UniqueIdentifier); submissionSetParamter.Value = currentDocument.SubmissionSetId; SqlParameter fileNameParam = logoCMD.Parameters.Add("@fileName", SqlDbType.VarChar, 100); fileNameParam.Value = currentDocument.FullFileName; int bufferSize = 100; // Size of the BLOB buffer. byte[] outbyte = new byte[bufferSize]; // The BLOB byte[] buffer to be filled by GetBytes. long retval; // The bytes returned from GetBytes. long startIndex = 0; // The starting position in the BLOB output. // Open the connection and read data into the DataReader. pubsConn.Open(); myReader = logoCMD.ExecuteReader(CommandBehavior.SequentialAccess); Array.Clear(data, 0, data.Length); if (myReader == null) { return; } while (myReader.Read()) { currentDocument.Size = (int)myReader.GetBytes(0, 0, null, 0, 0); int locationCounter = 0; // Reset the starting byte for the new BLOB. startIndex = 0; // Read the bytes into outbyte[] and retain the number of bytes returned. retval = myReader.GetBytes(0, startIndex, outbyte, 0, bufferSize); // Continue reading and writing while there are bytes beyond the size of the buffer. while (retval == bufferSize) { for (int i = 0; i < retval; i++) { data[locationCounter] = outbyte[i]; locationCounter++; } // Reposition the start index to the end of the last buffer and fill the buffer. startIndex += bufferSize; retval = myReader.GetBytes(0, startIndex, outbyte, 0, bufferSize); } } } catch (Exception ex) { throw ex; } finally { if (myReader != null) { myReader.Dispose(); myReader.Close(); myReader = null; } if (pubsConn != null) { pubsConn.Dispose(); pubsConn.Close(); pubsConn = null; } } I'm sure that there is a more efficient way to write this. And hasn't been fully tested. But the reference is finally working.