This is an excellent hint with the Async stuff! Happy this works, this makes things so much easier.
Ok, let’s consider downloading a file a solved problem.
I am trying to understand the concept of using Activities in C# in general. To me, it looks like that Coded Workflows are not intended to use the Visual Activities, C# is meant to use only the standard C# libraries like we know it from app development.
Example - in the Visual Xaml, parsing an Excel is done by using Excel Process Scope → Use Excel File → For Each Excel Row. I tried to rebuild that in C# and totally failed. Parsing Excel in C# is much easier done using a standard library like NuGet Gallery | ClosedXML 0.104.2
Meanwhile, I was able to decompose the generated code of visual flows using dotPeek. In the code, I could see that the OutArguments are passed in the form of magic strings between activities and extracted using dynamic expressions. This is not something I would use in a manually written C#.