I am creating a custom workflow activity in SharePoint 2013 Workflow. I need to get the set of user logins in a SharePoint site group so that I can send a mail to all users in the group.
In the workflow action list there is a action as "SPLookupGroupMembers". But it asks for a "GroupPrincipalId". The action "LookupPrincipalId" asks for a user name not a group name. How can I get the group ?