Hello :)

My link:
<%= link_to "fr", {:controller => controller.controller_name, :action => controller.action_name, :lang => 'fr', :id => params[:id]} %>
<%= link_to "fr", :url => "/main/research/?lang=#{params[:id]}" %>
Generates this:
http://127.0.0.1:3000/main/research?lang=fr

What I really need is this:
http://127.0.0.1:3000/main/research/?lang=fr

Where did I do the error please ?