CSV-Mapper upload problem

gistfile1.rb

class SalesController < ApplicationController
  include CsvMapper

  def csv_import
    results = CsvMapper.import(params[:dump][:file].original_filename) do
      map_to Sale
      after_row lambda{|row, sale| sale.save }

      start_at_row 1
      [start_date, country]
    end
    flash[:notice] = "Successfully uploaded file"
  end
end
  
In my Views:
<% form_for :dump, :url => {:controller => "sales", :action => "csv_import"}, :html => { :multipart => true } do |f| -%>
  <table>
   <tr>
     <td>
      <label for="dump_file">
        Select a CSV File :
      </label>
     </td>
     <td >
       <%= f.file_field :file -%>
     </td>
   </tr>
   <tr>
     <td colspan='2'>
       <%= submit_tag 'Submit' -%>
     </td>
   </tr>
 </table>
<% end -%>