这是参考：byte[] and efficiently passing by reference
此帖中的SqlDataReader：Getting binary data using SqlDataReader
在循环中，我正在调用数据库并返回一个大对象（varbinary[max]）。目前，我遇到了OutOfMemory例外，因此我正在尝试减少大对象堆（LOH）中的占用空间。
所以，我正在为我下载的最大文件创建一个字节数组，并添加一些填充以防万一。例如：
byte[] currentFile = new byte[largestFileSize * 1.1];
然后我传递了这个currentFile数据库方法。目前，我们使用EnterpriseLibrary访问数据库：
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();
}
这是对上面第二篇文章中列出的代码的修改。
以下是我的问题（如果我应该提出不同的问题，请随时纠正我）
如何在不创建新对象的情况下有效地重新填充byte[]？
上面的代码不使用创建新对象所需的CommandBehavior.SequentialAccess。如何将EnterpriseLibrary与CommandBehavior s一起使用？
我正在调用数据库并返回byte[]数组
更新
所以过了一段时间，我决定手动填充字节数组。该引用现已成功通过。
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;
}
}
我确信有更有效的方式来写这个。并没有经过全面测试。但参考文献终于有效了。
答案 0 :(得分：0)
所以我用以下代码替换了主循环：
if (myReader.Read())
{
currentDocument.Size = myReader.GetBytes(0, 0, null, 0, 0);
// Reset the starting byte for the new BLOB.
long startIndex = 0;
int bufferSize = 8196; // Size of the BLOB buffer.
byte[] outbyte = new byte[bufferSize]; // The BLOB byte[] buffer to be filled by GetBytes.
long bytesInBuffer = 0; // The bytes returned from GetBytes.
// Continue reading and writing while there are bytes beyond the size of the buffer.
while (startIndex < currentDocument.Size)
{
bytesInBuffer = myReader.GetBytes(0, startIndex, outbyte, 0, bufferSize);
Array.Copy(outbyte, 0, currentDocument.Data, startIndex, bytesInBuffer);
startIndex += bytesInBuffer;
}
}
立即行动。