I just had a strange experience where the .asmx file (the design file,
not the .asmx.cs file) had suddenly disappeared, which generated this
error. Try opening the .asmx file and see if it exists.
Okay, I finally figured it out. When I created the web service, I gave
it a virtual directory. Then I added the setup and ran the installer.
Unfortunately, I made the mistake of installing to the same virtual
directory that my project is in. So, when I uninstalled it, the contents
(.asax, .asmx, etc.) were removed.
