Add/Edit Project Server Resource Enterprise Custom Field with CSOM

Someone already asked this question, but no answer yet. 

https://social.msdn.microsoft.com/Forums/en-US/aa79c583-9247-4a76-9f1d-9369af310c96/how-to-addedit-project-server-resource-enterprise-custom-field-with-csom?forum=project2010custprog&prof=required

Using CSOM, I cannot figure out how to add a value for a Resource ECF if it is not already set.  There is no .SetCustomFieldValue() method as there is in a class such as Microsoft.ProjectServer.Client.Project.  Does anyone know how to do this?

Thanks, Saravanan PRS