title: WriteFile vs TransmitFile for large files that need to be deleted from the server after transfer
body: <p>I have to trigger user downloads of large files to a webbrowser, where I create the file to transfer on the server, then delete it immediately afterwards.  I've found enough examples to see that I should probably use Response.TransmitFile or Response.WriteFile... but have heard there are problems with both:</p>
  
  <p>WriteFile is synchronous, but it buffers the file in memory before sending it to the user.  Since I'm dealing with very large files, this could cause problems.</p>
  
  <p>TransmitFile doesn't buffer locally so it does work for large files, but it is asynchronous, so I can't delete the file after calling TransmitFile.  Apparently flushing the file doesn't guarantee that I can delete it either?</p>
  
  <p>What is the best way of dealing with this?</p>
  
  <p>There is the BinaryWrite also... could I loop through a file stream, copying it in segments?</p>