无法确定关系的主要结束。多个添加的实体可以具有相同的主键。

    public class Town
    {
        public int TownID
        {
            get;
            set;
        }

        public string TownName
        {
            get;
            set;
        }

        ObservableCollection<Building> buildings;

        [ForeignKey("TownID")]
        public ObservableCollection<Building> Buildings
        {
            get
            {
                if (buildings == null)
                    buildings = new ObservableCollection<Building>();

                return buildings;
            }
            set
            {
                buildings = value;
            }
        }
    }

    public class Building
    {
        public int BuildingID
        {
            get;
            set;
        }

        public string BuildingName
        {
            get;
            set;
        }

        public int TownID
        {
            get;
            set;
        }

        [ForeignKey("TownID")]
        public Town Town
        {
            get;
            set;
        }

        ObservableCollection<Worker> workers;

        [ForeignKey("BuildingID")]
        public ObservableCollection<Worker> Workers
        {
            get
            {
                if (workers == null)
                    workers = new ObservableCollection<Worker>();

                return workers;
            }
            set
            {
                workers = value;
            }
        }
    }

    public class Worker
    {
        public int WorkerID
        {
            get;
            set;
        }

        public string WorkerName
        {
            get;
            set;
        }

        public int BuildingID
        {
            get;
            set;
        }

        [ForeignKey("BuildingID")]
        public Building Building
        {
            get;
            set;
        }
    }

        static void Main(string[] args)
        {
            Model.CityCatalog cat = new Model.CityCatalog();

            Town MyTown = cat.Towns.Take(1).First();

            int iBuildings = 0;
            while (iBuildings < 2)
            {
                Building b = new Building()
                {
                    BuildingName = "Town Center" + (++iBuildings).ToString(),
                    Town = MyTown
                };

                cat.Buildings.Add(b);

                int iWorkers = 0;
                while (iWorkers < 2)
                {
                    Worker w = new Worker()
                    {
                        WorkerName = "Worker " + (++iWorkers).ToString(),
                        Building = b
                    };

                    cat.Workers.Add(w);
                }

            }
            cat.SaveChanges();
        }

执行上述公司de给出错误

Executing the above code gives error

无法确定'CodeFirstNamespace.Building_Workers'关系的主要结尾。多个添加的实体可能具有相同的主键。

Unable to determine the principal end of the 'CodeFirstNamespace.Building_Workers' relationship. Multiple added entities may have the same primary key.

 如果在Building循环中执行cat.SaveChanges（），则可以很好地保存数据库。

 If you execute cat.SaveChanges() inside Building loop it saves fine to the database.

 但是，保存多个建筑物会出现上述错误。

 but, saving multiple Buildings gives above error.