What exactly is a "module"?

[Korporal]

I've seen the term used in .Net since day one, but I've never really understood what it is exactly, unlike an Assembly which has various classes representing it, a Module seems more nebulous, I've no idea what it is or why the term is even used.

[CyrusNajmabadi]

https://learn.microsoft.com/en-us/dotnet/standard/assembly/

In .NET and .NET Framework, you can build an assembly from one or more source code files. In .NET Framework, assemblies can contain one or more modules.

https://learn.microsoft.com/en-us/dotnet/framework/app-domains/build-multifile-assembly

[CyrusNajmabadi]

unlike an Assembly which has various classes representing it

This is not really accurate. An assembly always has at least one module, and it contains those classes. It can have more modules stitched together. You'll see this in reflection with things like the ModuleBuilder type. It's also exposed in Roslyn in our apis as well.

I've no idea what it is or why the term is even used.

Consider coming to our discords for these sorts of free form questions. You'll get responses and links normally in minutes or seconds.

[huoyaoyuan]

Historically, there was an idea that an assembly can be distributed as multiple files via Internet, and only executed part will be downloaded. The idea was then abandoned in the new century because directly executing code from Internet is totally horrible.

[Korporal]

unlike an Assembly which has various classes representing it

This is not really accurate. An assembly always has at least one module, and it contains those classes. It can have more modules stitched together. You'll see this in reflection with things like the ModuleBuilder type. It's also exposed in Roslyn in our apis as well.

It is accurate actually, an assembly is represented by the Assembly class and numerous other Assembly related classes.

[CyrusNajmabadi]

As does a module:

https://learn.microsoft.com/en-us/dotnet/api/system.reflection.module?view=net-8.0
https://learn.microsoft.com/en-us/dotnet/api/system.reflection.assembly.getmodules?view=net-8.0
https://learn.microsoft.com/en-us/dotnet/api/system.type.module?view=net-8.0

Etc :)

You're thinking about the flattened view of things. But i'm explaining that that flattened view is precisely flattened from teh module-based view that it is actually can be constructed from :)

Since you asked what modules were, it seems like getting this information would be valuable since it explains just that :)