using (systemEntities myEntity = new systemEntities())
                    {
            //Company oluşturmaya başlıyoruz
                        companies mCompany = new companies();
                        mCompany.CompanyName = "New Company";
                        mCompany.Status = 1;
                        myEntity.AddTocompanies(mCompany);//Ekle

            //user oluşturmaya başlıyoruz
                        users mUser = new users();
                        mUser.CompanyRef = mCompany.RID;//eklenen company'nin ID'si

                        myEntity.AddTousers(mUser);//Ekle
                        myEntity.SaveChanges();//kaydet
                    }


EXCEPTION

System.Data.UpdateException: An error occurred while updating the entries. See the inner exception for details. ---> System.ArgumentException: The specified value is not an instance of a valid constant type
Parameter name: value
   at System.Data.Common.CommandTrees.ExpressionBuilder.Internal.ArgumentValidation.ValidateConstant(Object value)
   at System.Data.Mapping.Update.Internal.DynamicUpdateCommand.CreateCommand(UpdateTranslator translator, Dictionary`2 identifierValues)
   at System.Data.Mapping.Update.Internal.DynamicUpdateCommand.Execute(UpdateTranslator translator, EntityConnection connection, Dictionary`2 identifierValues, List`1 generatedValues)
   at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter)
   --- End of inner exception stack trace ---
   at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter)
   at System.Data.EntityClient.EntityAdapter.Update(IEntityStateManager entityCache)
   at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options)
   at System.Data.Objects.ObjectContext.SaveChanges()
   at Register.btnOlustur_Click(Object sender, EventArgs e) in c:\Users\.......