无法使用csom使用查找表GUID更新任务或项目上的CustomField

Question

Has someone managed to update custom fields programmatically on a Task or a Project which uses lookup values? I'm using CSOM, code is below, c#. Lookup Custom Field does update but field set to blank, overwriting previous value entered using Web App. Updates to 'Text' Custom fields work fine.

private void SendCode()
{
    ProjectContext context;
    using (context = new ProjectContext(ConfigurationManager.AppSettings["psUrl"]))
    {
        context.Load(context.Projects,
            pj => pj.Include(
                p => p.Id,
                p => p.Name));
        context.Load(context.CustomFields,
            lts => lts.Include(
                lt => lt.Name,
                lt => lt.InternalName));

        context.ExecuteQuery();
        // Output Status is a Custom Filed referring to a lookup table called Output Status with 6 status values
        string customFieldName = "Output Status";
        // A routine to get the correct GUID from the lookup Table
        object customFieldValue = new Guid("1aded2bc-67ad-49e4-9c52-a9dca4ea09a5");
        foreach (PublishedProject pp in context.Projects)
        {
            DraftProject proj2Edit = pp.CheckOut().IncludeCustomFields;
            context.Load(proj2Edit.Tasks,
                ts => ts.Include(
                    t => t.Id,
                    t => t.Name,
                    t => t.CustomFields,
                    t => t.OutlineLevel,
                    t => t.IsSummary));
            context.ExecuteQuery();
            var cfInternalName = context.CustomFields.First(cf => cf.Name == customFieldName).InternalName;
            DraftTask newTask = proj2Edit.Tasks.First(t => t.Name == "REI and PPR Monitoring");
            newTask[cfInternalName] = customFieldValue;  // How should you be setting the GUID?
            proj2Edit.Publish(true);
            QueueJob qJob = context.Projects.Update();
            JobState jobState = context.WaitForQueue(qJob, QueueTimeout);
        }
    }
}

Answer 1

Found a solution. You do not pass the lookup GUID but the Intername of the LookupEntry as well. The value should be something like 'Entry_...'

These posts were very helpful: https://social.msdn.microsoft.com/Forums/en-US/c91644b7-3c0f-4d65-a8d7-2dec128d1dcf/project-lookup-custom-field-update-with-csom?forum=project2010custprog

https://social.msdn.microsoft.com/Forums/en-US/b4d3ee63-965b-4489-8b34-6ad53b128553/csom-update-custom-field-based-on-lookup-table?forum=project2010custprog