Download link not returning proper byte stream - asp.net

Question

I'm retrieving a file from a database server and allowing the user to download it. The problem is, I'm not getting the same byte stream out as I've read from the server.
I have confirmed (through lots of response.write) that I've received the right array of bytes, they're in the right order, etc...
Here's the code for the download st.FileContents is a byte[]:
Response.Clear();
Response.AddHeader("Content-Disposition",
"attachment; filename=" + st.FileName);
Response.AddHeader("Content-Length", st.FileSize.ToString());
Response.ContentType = "application/octet-stream";
Response.Write(new System.Text.ASCIIEncoding()
.GetString(st.FileContents)); // Problem line
Response.End();
I've tried a few ways of converting that byte [] to a string, and none give the results I need. Instead of the expected stream of bytes as:
FF D8 FF E0 1E D0 4A 46 58 58 00 10 FF D8 FF DB
(yes, that's the start of a jpeg image)
I wind up with something like:
C3 BF C3 98 C3 BF C3 A0 1E C3 90 4A 46 58 58 00
The first 6 bytes get mangled into 10 completely different bytes. What gives?
Edit
The answer is, of course, to use BinaryWrite instead of Write.

Answer 1

You shouldn't be treating binary data as strings. In this example, ASCII encoding only supports characters in range 0-127, so any bytes that do not fall into that range are treated as invalid and replaced with a question mark. Use HttpResponse.BinaryWrite instead:
Response.BinaryWrite(st.FileContents);