How do you debug a single ASPX file?

I am somewhat new to ASPX files, but I am not new to C#.

I figured that all c# projects were run on the server as compiled code. And so there was some sort of binary file somewhere somehow or maybe a XAP file like they have with silverlight.

But it seems that this is not the case. it seems that, sometimes, you can have an ASPX file along with the code-behing C Sharp file and it runs just like a PHP file. For starters, is that right? Am I right so far?

Now, if I was the owner of both the ASPX file and the CSHARP code-behind file, how would I go about debugging it in Visual Studio?

How do I run the code?

My point is that there is no project to load. There is only a file.

After setting a break point, there is nothing to run.

I have tried attaching to the browser that has the aspx code loaded but then the breakpoints become inactive.

the file is

and out on the server there is just the aspx file and the accompanying .cs file

That is all there is. There is no solution file, there is no default.aspx file there is nothing else in the that directory apart from other .aspx files and aspx.cs files.

If it was a web form, there would be a project file and and or a solution file. There would be something compiled, right? There is nothing like that. there are no dll files

I think I need to do the following. I need to run the code locally through "localhost" and attach the process through the debugger. How do I run the localhost?