Question

Does anyone know how WebClient.DownloadFileAsync is implemented ?
I have a few questions about this:

1. Is the stream returned saved in memory until the whole file downloads or is it buffered straight into a temp file ( and then copied to the correct path) ? or straight into the file indicated ?

2. Writing a simple WCF rest service to answer these calls would require the following:

   set response headers - Content-Type: application/octet-stream  
                          Content-Length: 3 
                          Content-Disposition: Attachment;
                          filename=SomeFileName.jpeg 
   

   and return a byte[]

Am I missing anything ?

Answer 1

1. The response stream is read in chunks and those chunks are directly written to the output file stream and the entire file is not loaded in memory.
2. The WebClient doesn’t really care what headers does the server send. It reads the response stream and saves it to the output file in chunks.