Files in libraries or multiple-file applications must begin with a namespace or module declaration

Files in libraries or multiple-file applications must begin with a namespace or module declaration, e.g. 'namespace SomeNamespace.SubNamespace' or 'module SomeNamespace.SomeModule'

error at #r @"bin/fszmq.dll"

is it correct to add a module mainmod

after add module mainmod, got error

#r directives may only occur in F# script files (extensions .fsx or .fsscript). Either move this code to a script file, add a '-r' compiler option for this reference or delimit the directive with '#if INTERACTIVE'/'#endif'.

after nuget install fszmq -Pre

The file zhelpers.fs is above or below ? Because is Visual Studio F# sources files are compiled in the order they are displayed in VS's solution explorer, from top to bottom.

So I deduce the zhelpers.fs is under program.fs, so for F#'s compiler, the file doesn't exist in program.fs.

You can fix it for example by removing equal sign from 'module zhelpers=' in the second file.