Reference error trying to build sample custom activities library: system.activities not found


Trying to figure out using custom external assemblies etc. One of the example files stipulates that the Visual Studio project have:

using System.Activities.Presentation.Metadata;

This is necessary to implement the following class:

// Declare dummy register metadata class to force UiPath to load this assembly
public class RegisterMetadata : IRegisterMetadata
public void Register()


Angry buzzer noise:
The type or namespace name ‘Activities’ does not exist in the namespace ‘System’ (are you missing an assembly reference?)

I do see the System.Activities.Presentation.Metadata namespace in Studio.

Most vexing.



Never mind, I think I figured it out.