How to programmatically change a user field restricted to a single Sharepoint group in CSOM

Question

It possible in CSOM to change a user field to restrict the People picker to a single Sharepoint Group?

Answer 1

I've found this solution:

        string weburl = "http://piero.it/sites/pdvc/TestCon2004";
        string listName = "Agenda";
        string fieldName = "Utente";
        string groupName = "CreatoriRaccolte";

        using (ClientContext clientContext = new ClientContext(weburl))
        {
            Group group = clientContext.Web.SiteGroups.GetByName(groupName);
            clientContext.Load(group);
            clientContext.ExecuteQuery();

            List list = clientContext.Web.Lists.GetByTitle(listName);
            clientContext.Load(list, l => l.Fields);
            clientContext.ExecuteQuery();

            Field field = list.Fields.GetByInternalNameOrTitle(fieldName);
            FieldUser fieldUser = clientContext.CastTo<FieldUser>(field);
            fieldUser.SelectionMode = FieldUserSelectionMode.PeopleOnly;
            fieldUser.SelectionGroup = group.Id;
            fieldUser.Update();
            clientContext.Load(fieldUser);
            clientContext.ExecuteQuery();
        }