webapi2.

var form = HttpContext.Current.Request.Form;
 var sku_input = form["username"];

 HttpFileCollection files = HttpContext.Current.Request.Files;
            var keys = HttpContext.Current.Request.Files.Keys;

  var fileName = HttpContext.Current.Request.Files[i].FileName;
                var fileStream = files[i].InputStream;

MVC：

var aaa =   Request.Form["username"];


var files = Request.Files;