A couple of clarifications: 

To refactor something is to alter its internal structure without changing its external behavior.  You can access source code by using a decompiler, but it is often not worth investing a lot of time into because the decompiler has made formatting decisions that make most code difficult to read for humans (as it was already stripped down for machine only readability).  

Refactoring is usually only done to either improve the performance or readability of the code, so you are starting at a loss if your goal is the latter.  My guess is you need to go in and tweak some functionality, in which case a decompiler is really the only way to go, but finding the source code and keeping good track of source code is probably a better bet.  When we deploy code to production we include a ReadMe.txt file with it indicating where to look for the source code.

Additionally, some asp.net files are not compiled into .dll's.  Typically .dlls only include files ending in .vb or .cs.  You'll still need to have access to and include non-compiled pages like .aspx and .ascx files, but these will also be on your server.

A good free alternative to .NET Reflector is to use Telerik's [Just Decompile](http://www.telerik.com/products/decompiler.aspx) which has an option to recreate the .proj file from the compiled code.

Scenario: I have access to an already published ASP.NET application running on a remote web server.  The directory structure looks like this:

![enter image description here][1]


  [1]: http://i.stack.imgur.com/Zwvs6.png

I do not have access to the project/solution files as far as I know.  Specifically, I cannot find specific C# code-behind files that I need to modify.

Is it possible to rebuild this project with minimal effort using only the published code?