title: How to add/edit related entity while staying on form
body: <p>As I'am a newcomer to Web programming I'am stuck with quite a common use case. To keep it simple I'll use Invoice example. While entering Invoice I can select existing customer from DropDownList. But if customer don't exist I have to create it, and then select it. Surely I can navigate to Customers, add a new customer then go back to Invoice and start from begining but this is surely not a way to go. I'am sure there is some sort of 'best practice' way to deal with it as instead Invoice there could be a long input form with many realated records and losing populated fields could not be an option.</p>
  
  <p>In WPF I would use modal views. Supposedly the same approach could be used here but I haven't found similar example maybe using wrong terms. </p>
  
  <p>I'am aware that jQuery/javascript is a way to go but still dont't now what would be 'best practice' look alike. Also, is there some good UI aproach for alike inputs to go without javascript?</p>
  
  <p>Can someone turn me toward right direction and release me from too many guesses?</p>