Master-detail scenario-Entity data Model

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ADO.NET

hi,
I am using entity data model and i have master-detail scenario.(Patient-PatientAddresses)

Everything is going on fine if i am updating any data either in master table or detail table.

But when i am going to insert a new detail record while updating master entity, it gives me following error :
"An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key."

I googled so much, but not getting proper idea.

Here is my code :

using (var context = new Entities())
            {
                try
                {
                    var record = (from p in context.Patient.Include("PatientAddress")
                                  where p.PatientId == patient.PatientId
                                  select p).FirstOrDefault();
                    
                    if (record == null)
                    {
                        context.AddToPatient(patient);
                    }
                    else
                    {
                        foreach (var item in patient.PatientAddress)
                        {
                            if (item.EntityKey == null)
                            {
                                context.AddToPatientAddress(item); // <--Throws Exception here.
                                continue;
                            }
                            context.ApplyPropertyChanges("PatientAddress", item);
                        }
                        context.ApplyPropertyChanges("Patient", patient);
                    }
                    context.SaveChanges();
                    return true;
                }
                catch
                {
                    return false;
                }
            }

Any suggessions is appreciated.