how to redirect paypal sandbox to localhost (asp.net's ) after successful transaction ? is it possible ? silly question but may be ....................

You need to include the markup in your post that you've tried. I think you need to include the return url hidden field that contains the absolute URI of your webapp's resource/page.

<form ....>
  .....
  <input type="hidden" 
         name="return" value="http://localhost/WebSite/page1.aspx" />
  ....
</form>
Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.