I'm trying to uplaod a file using

  <%
    using (Ajax.BeginForm("LoadFile", new AjaxOptions { }))
    {
%>
<input type="file" is="Fichier" name="fichier" />
<%
    }
%>

 and in my controller Request.Files is always empty. If i change to Html.BeginForm, the file is uploaded fine...

what am I missing?

thx

 Files can not be uploaded using AJAX. The XmlHttpRequest doesn't support it (for very valid security reasons). You will have to use something like SwfUpload or upload inside an iframe to simulate it.