Rails Import CSV - All Values 'Nil'
===

I'm learning how to import csv to a rails application. However, when i run the application, all the values turned out to be 'nil'. May I know what is wrong with my codes below?

<h3>Controller</h3>

    def import_csv
        @list = List.find(params[:list_id])
        @lists = List.all
        
    respond_to do |format|
    @csv=params[:file]
    @n=0
    CSV.parse(@csv).each do | row |
      @user_new = User.new
      @user_new.first_name = row[0]
      @user_new.last_name = row[1]
      @user_new.email = row[2]
      @user_new.address = row[3]
      @user_new.city = row[4]
      @user_new.state = row[5]
      @user_new.zipcode = row[6]
      @user_new.country = row[7]
      @user_new.notes = row[8]
      @user_new.birthday = row[9]
      @user_new.home_number = row[10]
      @user_new.mobile_number = row[11]
      @user_new.list_id = @list.id
      @user_new.save

      @n=@n+1
      GC.start if @n%50==0
      flash[:notice] = "CSV Imported Successfully, with  #{@n} records"                                
    end
    
      format.html { redirect_to lists_url }
      format.json { head :no_content }
    end

      end

<h3>View</h3>

    <%= form_for(:list, :url => list_import_csv_path(@list), :method => :get, :html => {:multipart => true}) do |f| %>
     <table>
    	<tr>
    		<td><label for="dump_file">Select a CSV File :</label></td>
    		<td ><%= file_field_tag :file %></td>
    	</tr>
    	<tr>
    		<td colspan='2'><%= submit_tag 'Submit' %></td>
    	</tr>
    </table>
    <% end %>