For any versions of Visual Studio you have to these steps
- Go to Tools > Options
- Go to Debugging > Edit and Continue > Check Enable Edit and Continue
- Go to Debugging > General > Check Break all process when one process break
- Go to Debugging > General > Check Require source files to exactly match the original version
For Web Application Project, you have to do these additional steps
- Go to Web Application Project properties
- Make sure your project in Debug Mode by Build > Active Configuration Mode > Select Active (Debug) and Uncheck Optimize Code
- Make sure your using Visual Studio Internal Web Server (Cassini) by Web > Check Use Visual Studio Development Server
- Enabling Edit and Continue by Web > Check Edit and Continue
Additional for Visual Studio 2010, you have to disabled Intellitrace feature by
- Go to Tools > Options
- Go to Intellitrace > Uncheck Enable Intellitrace

I am debugging a web application and applied all settings mentioned above. Thanks to these settings I am able to modify my source code. But after doing this Visual Studio insists on restarting the web application which takes quit a long time. Obviously, I am looking for a way the web application and immediatly seeing the change on all affected web page without restarting.
Is there a way to do that ?
Edward