ASP.NET Streaming Output: 1 single big chunk vs X smaller chunks? - asp.net

Question

Using .NET 4.0, IIS 7.5 (Windows Server 2008 R2). I would like to stream out a binary content of about 10 MB. The content is already in a MemoryStream. I wonder if IIS7 automatically chunks the output stream. From the client receiving the stream, is there any difference between these two approaches:
//#1: Output the entire stream in 1 single chunks
Response.OutputStream.Write(memoryStr.ToArray(), 0, (int) memoryStr.Length);
Response.Flush();
//#2: Output by 4K chunks
byte[] buffer = new byte[4096];
int byteReadCount;
while ((byteReadCount = memoryStr.Read(buffer, 0, buffer.Length)) > 0)
{
Response.OutputStream.Write(buffer, 0, byteReadCount);
Response.Flush();
}
Thanks in advance for any help.
I didn't try your 2nd suggestion passing the original data stream. The memory stream was indeed populated from a Response Stream of a Web Request. Here is the code,
HttpWebRequest webreq = (HttpWebRequest) WebRequest.Create(this._targetUri);
using (HttpWebResponse httpResponse = (HttpWebResponse)webreq.GetResponse())
{
using (Stream responseStream = httpResponse.GetResponseStream())
{
byte[] buffer = new byte[4096];
int byteReadCount = 0;
MemoryStream memoryStr = new MemoryStream(4096);
while ((byteReadCount = responseStream.Read(buffer, 0, buffer.Length)) > 0)
{
memoryStr.Write(buffer, 0, byteReadCount);
}
// ... etc ... //
}
}
Do you think it can safely pass the responseStream to Response.OutputStream.Write() ? If yes, can you suggest an economic way of doing so? How to send ByteArray + exact stream length to Response.OutputStream.Write()?

Answer 1

The second option is the best one as ToArray will in fact create a copy of the internal array stored in the MemoryStream.
But, you can also preferably use memoryStr.GetBuffer() that will return a reference to this internal array. In this case, you need to use the memoryStr.Length property because the buffer returned by GetBuffer() is in general bigger than the stored actual data (it's allocated chunk by chunk, not byte by byte).
Note that it would be best to pass the original data as a stream directly to the ASP.NET outputstream, instead of using an intermediary MemoryStream. It depends on how you get your binary data in the first place.
Another option, if you serve the exact same content often, is to save this MemoryStream to a physical file (using a FileStream), and use Response.TransmitFile on all subsequent requests. Response.TransmitFile is using low level Windows socket layers and there's nothing faster to send a file.