How does the setup.exe for a ClickOnce published application know how to get the prerequisites?

Question

I'm researching ClickOnce to help maintain a .Net 3.5 legacy application and I haven't really found anything that explains how a ClickOnce published app figures out what prerequisites need to be installed. The setup.exe file is downloaded from a website so that anyone can install the application. What I need to know is if the prerequisite information is baked into the setup.exe file or if it reaches out to the server and get that information from the app.manifest or something?

Answer 1

Well, setup.exe is template unmanaged executable file. What does template means? Every time you publish you have a simulator assembler instructions in published setup.exe file. Only PE file resources has changes every build (see: PE file format), so Visual Studio updates resources on publish and there is what you want. If you wanna find out prerequisite there, you can download any PE Resource Viewer (For example Resource Hacker) and check for SETUPCFG resource name. There is some pseudo language for prerequisite, here is my example below:

By the way you can find out there download URLs.