CRM 2011 plugin - Attribute ‘xxxx’ cannot be NULL

I was getting the “Attribute ‘xxxx’ cannot be NULL” error while attempting to update a CRM entity. What I was trying to do was to use the Entity object to perform an update and I think that was causing an error as the attribute ‘xxxx’ which was a required attribute did not have a value. But in my case, all I was trying to do was to update one of the attributes of that entity.

The original code that did not work:

Incident incident = new Incident();
incident.IncidentId = incidentGuid;
contact.new_Contact_Incident_Id = incident;

I was able to get my code working by using the EntityReference object. Here is the working code:

EntityReference incidentRef = new EntityReference(Incident.EntityLogicalName, incidentGuid);
contactEntity[“new_contact_incident_id”] = incidentRef;
PluginContext.OrganizationService.Update(contactEntity);