C# Plugin Check whether entity contains field fails - given key not in the dictionary

Entity eContact = service.Retrieve("contact", _sender.Id, new ColumnSet("parentcustomerid"));
tracer.Trace(eContact.Contains("parentcustomerid").ToString()); //returns false

foreach (KeyValuePair<string, object> att in eContact.Attributes) //only gives contact id
    if (att.Value.GetType() == typeof(EntityReference))
        tracer.Trace(att.Key + ": " + ((EntityReference)att.Value).Name);
    else
        tracer.Trace(att.Key + ": " + att.Value.ToString());

if (eContact.Contains("parentcustomerid") && eContact["parentcustomerid"] != null && ((EntityReference)eContact["parentcustomerid"]).LogicalName == "account")//Given Key not in Distionary error
{
    tracer.Trace("Set Account");
    eCase["dsg_account"] = (EntityReference)eContact["parentcustomerid"];
}