How to convert Form of old Rails in Rails 3.2

Question

I want to implement this simple form but its in old rails. Can somebody help me out to convert it in Rails 3.2?

<%= start_form_tag ({:action => 'uploadfile'},:multipart => true) %>
<p><label for="upload_file">Select File</label> : 
<%= file_field 'upload', 'datafile' %></p>
<%= submit_tag "Upload" %>
<%= end_form_tag %>

Answer 1

<%= form_for(:upload, :url => { :action => "uploadfile" }, :multipart => true) do |form| %>
  <p><%= form.label :datafile, "Select File" %> :
  <%= form.file_field 'datafile' %></p>
  <%= form.submit "Upload" %>
<% end %>