Upload file via input control and empty File Collection in request

when we uplaod files via html input control, sometimes we get Empty file collection on server side, i faced this issue in one of my Sharepoint projects and resolved with adding

Page.Form.Enctype = "multipart/form-data";

in page load.

http://stackoverflow.com/questions/1226612/sharepoint-webpart-upload-file-whitout-using-runat-server