Asynchronous use of webclient to transfer files

I have an objective to transfer some files which can be pdf, jpg and xml from one location to another. I am creating a handler based API for that. What could be the best approach for doing it? Should i return a byte array so that the client can pick the byte array and convert it back to file? Also the max file size I need to handle is 18 MB, so i have to make sure that the sizes are properly handled. Should I do an asynchronous transfer for that? If there 开发者_JAVA技巧is some sample code available it would be great.

i got it done using this: http://blog.net-tutorials.com/2009/03/16/how-to-download-a-file-from-the-internet-with-c/ but it has another issue which i mentioned in another question here:

WebClient.DownloadFileAsync downloading the file on server