I have a View in which the user is able to upload a file to the server.
In this view I also have 2 buttons: one to Upload a file and other to Download the last file
To generate a POST request for the upload, use the File Input form element and just post back to the server ala normal.
http://www.w3schools.com/jsref/dom_obj_fileupload.asp
Have a look at this blog post from Scott Hanselman. http://www.hanselman.com/blog/ABackToBasicsCaseStudyImplementingHTTPFileUploadWithASPNETMVCIncludingTestsAndMocks.aspx