As discussed in Geocortex Workflow Server, deploying a custom activity to Geocortex Workflow Server involves creating a .NET project that generates compatible assemblies and then copying them to the build folder. Adding a third party assembly is as simple as adding the library to your .NET project and then ensuring it is copied along with the user defined code.
Any nuget package can be added to the project and used in custom activities.
Build the project to output the project assemblies. Follow the instructions to Deploy the Activity. Ensure that you locate and copy the third party assemblies. If you don't see them in the build output folder, review the instructions and ensure you have followed all the steps.
An important step not to miss is adding the
CopyLocalLockFileAssemblies attribute to the
.csproj file if you created a .NET Standard class library. Without this attribute, your nuget package reference assemblies will not be output to the build folder.