How can I update the Target Group Conditions in a Component Presentation using the Core Service in SDL Tridion 2013?

Question

I am trying to update the Target Groups conditions in the component presentations of a page using the Core Service. I am in SDL Tridion 2013 and here is the code I am using:

try
{
    OpenSession(serviceInput.Server, serviceInput.User);
    page = session.Read(context.PageUri, new ReadOptions()) as PageData;
    if (page!=null)
    {
        page = session.CheckOut(context.PageUri, true, new ReadOptions()) as PageData;
        List<TargetGroupConditionData> tgs = new List<TargetGroupConditionData>();
        foreach (ComponentPresentationData cp in page.ComponentPresentations)
        {
            if (cp.Component.IdRef.Equals(context.ComponentUri) &&
                cp.ComponentTemplate.IdRef.Equals(context.TemplateUri))
            {
                foreach (MobileTargetGroupInput input in groups)
                {
                    TargetGroupConditionData data = new TargetGroupConditionData()
                    {
                        Negate = input.Negate,
                        TargetGroup = new LinkToTargetGroupData() {IdRef = input.Uri}
                    };
                    tgs.Add(data);
                }
                cp.Conditions = tgs.ToArray();
            }
        }

        session.CheckIn(context.PageUri,true,string.Empty,null);

        result.Success = true;
        result.Message = String.Format("Page {0} updated.", context.PageUri);
    }

    return result;
}
catch (Exception ex)
{
    result.Success = false;
    result.Message = ex.Message;
    return result;
}
finally
{
    CloseSession();
}

The code does not fail at all, but the page in question, never gets updated. Can you guys help me out? I don't understand what I am missing.

Answer 1

I figured it out:

I was missing the .Save call before the .CheckIn. So the code should be like this:

try
{
    OpenSession(serviceInput.Server, serviceInput.User);
    page = session.Read(context.PageUri, new ReadOptions()) as PageData;
    if (page != null)
    {
        page = session.CheckOut(context.PageUri, true, new ReadOptions()) as PageData;
        List<TargetGroupConditionData> tgs = new List<TargetGroupConditionData>();
        foreach (ComponentPresentationData cp in page.ComponentPresentations)
        {
            if (cp.Component.IdRef.Equals(context.ComponentUri) &&
                cp.ComponentTemplate.IdRef.Equals(context.TemplateUri))
            {
                foreach (MobileTargetGroupInput input in groups)
                {
                    TargetGroupConditionData data = new TargetGroupConditionData()
                    {
                        Negate = input.Negate,
                        TargetGroup = new LinkToTargetGroupData() {IdRef = input.Uri}
                    };
                    tgs.Add(data);
                }
                cp.Conditions = tgs.ToArray();
            }
        }  

        // I WAS MISSING THIS LINE!
        session.Save(page, null);

        session.CheckIn(context.PageUri,true,string.Empty,null);

        result.Success = true;
        result.Message = String.Format("Page {0} updated.", context.PageUri);
    }

    return result;
}
catch (Exception ex)
{
    result.Success = false;
    result.Message = ex.Message;
    return result;
}
finally
{
    CloseSession();
}