WCF服务远程调用Linq出现异常

一直以来都在学习中，所以也没有什么好文章献给大家，这次小弟也是来提问的，Dudu觉得不合适可以从首页撤掉。不过本人认为让更多的人看到问题也是不错的。
问题如下：
    建立了Book数据库，库中有三张表Orders，Products，Remarks。其中Orders的字段Oid是Products字段Poid的主键，意思是这两张表组成了主外键关系。Remarks是一张独立的表。利用Linq To SQL设计器生成了三张表的实体类。并将三个实体类暴露给客户端（[DataContract]）.代码如下：

Orders类：

Code
  1[Table(Name="dbo.orders")]
  2    [DataContract(Name = "Orders", Namespace = "http://www.lgx.OrderLinq")]
  3    public partial class order : INotifyPropertyChanging, INotifyPropertyChanged
  4    {
  5        
  6        private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(String.Empty);
  7        
  8        private int _oid;
  9        
 10        private System.Nullable<decimal> _totalPrice;
 11        
 12        private System.DateTime _odate;
 13        
 14        private EntitySet<product> _products;
 15        
 16    Extensibility Method Definitions#region Extensibility Method Definitions
 17    partial void OnLoaded();
 18    partial void OnValidate(System.Data.Linq.ChangeAction action);
 19    partial void OnCreated();
 20    partial void OnoidChanging(int value);
 21    partial void OnoidChanged();
 22    partial void OntotalPriceChanging(System.Nullable<decimal> value);
 23    partial void OntotalPriceChanged();
 24    partial void OnodateChanging(System.DateTime value);
 25    partial void OnodateChanged();
 26    #endregion
 27        
 28        public order()
 29        {
 30            this._products = new EntitySet<product>(new Action<product>(this.attach_products), new Action<product>(this.detach_products));
 31            OnCreated();
 32        }
 33        
 34        [Column(Storage="_oid", AutoSync=AutoSync.OnInsert, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
 35        [DataMember(Order=0)]
 36        public int oid
 37        {
 38            get
 39            {
 40                return this._oid;
 41            }
 42            set
 43            {
 44                if ((this._oid != value))
 45                {
 46                    this.OnoidChanging(value);
 47                    this.SendPropertyChanging();
 48                    this._oid = value;
 49                    this.SendPropertyChanged("oid");
 50                    this.OnoidChanged();
 51                }
 52            }
 53        }
 54        
 55        [Column(Storage="_totalPrice", DbType="Decimal(18,3)")]
 56        [DataMember(Order = 1)]
 57        public System.Nullable<decimal> totalPrice
 58        {
 59            get
 60            {
 61                return this._totalPrice;
 62            }
 63            set
 64            {
 65                if ((this._totalPrice != value))
 66                {
 67                    this.OntotalPriceChanging(value);
 68                    this.SendPropertyChanging();
 69                    this._totalPrice = value;
 70                    this.SendPropertyChanged("totalPrice");
 71                    this.OntotalPriceChanged();
 72                }
 73            }
 74        }
 75        
 76        [Column(Storage="_odate", DbType="DateTime NOT NULL")]
 77        [DataMember(Order = 2)]
 78        public System.DateTime odate
 79        {
 80            get
 81            {
 82                return this._odate;
 83            }
 84            set
 85            {
 86                if ((this._odate != value))
 87                {
 88                    this.OnodateChanging(value);
 89                    this.SendPropertyChanging();
 90                    this._odate = value;
 91                    this.SendPropertyChanged("odate");
 92                    this.OnodateChanged();
 93                }
 94            }
 95        }
 96        
 97        [Association(Name="order_product", Storage="_products", OtherKey="poid")]
 98        [DataMember(Order = 3)]
 99        public EntitySet<product> products
100        {
101            get
102            {
103                return this._products;
104            }
105            set
106            {
107                this._products.Assign(value);
108            }
109        }
110        
111        public event PropertyChangingEventHandler PropertyChanging;
112        
113        public event PropertyChangedEventHandler PropertyChanged;
114        
115        protected virtual void SendPropertyChanging()
116        {
117            if ((this.PropertyChanging != null))
118            {
119                this.PropertyChanging(this, emptyChangingEventArgs);
120            }
121        }
122        
123        protected virtual void SendPropertyChanged(String propertyName)
124        {
125            if ((this.PropertyChanged != null))
126            {
127                this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
128            }
129        }
130        
131        private void attach_products(product entity)
132        {
133            this.SendPropertyChanging();
134            entity.order = this;
135        }
136        
137        private void detach_products(product entity)
138        {
139            this.SendPropertyChanging();
140            entity.order = null;
141        }
142    }

Products类：

Code
  1[Table(Name="dbo.products")]
  2    [DataContract(Name = "Products", Namespace = "http://www.lgx.OrderLinq")]
  3    public partial class product : INotifyPropertyChanging, INotifyPropertyChanged
  4    {
  5        
  6        private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(String.Empty);
  7        
  8        private int _pid;
  9        
 10        private int _poid;
 11        
 12        private string _pName;
 13        
 14        private decimal _price;
 15        
 16        private System.DateTime _pdate;
 17        
 18        private EntityRef<order> _order;
 19        
 20    Extensibility Method Definitions#region Extensibility Method Definitions
 21    partial void OnLoaded();
 22    partial void OnValidate(System.Data.Linq.ChangeAction action);
 23    partial void OnCreated();
 24    partial void OnpidChanging(int value);
 25    partial void OnpidChanged();
 26    partial void OnpoidChanging(int value);
 27    partial void OnpoidChanged();
 28    partial void OnpNameChanging(string value);
 29    partial void OnpNameChanged();
 30    partial void OnpriceChanging(decimal value);
 31    partial void OnpriceChanged();
 32    partial void OnpdateChanging(System.DateTime value);
 33    partial void OnpdateChanged();
 34    #endregion
 35        
 36        public product()
 37        {
 38            this._order = default(EntityRef<order>);
 39            OnCreated();
 40        }
 41        
 42        [Column(Storage="_pid", AutoSync=AutoSync.OnInsert, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
 43        [DataMember(Order=0)]
 44        public int pid
 45        {
 46            get
 47            {
 48                return this._pid;
 49            }
 50            set
 51            {
 52                if ((this._pid != value))
 53                {
 54                    this.OnpidChanging(value);
 55                    this.SendPropertyChanging();
 56                    this._pid = value;
 57                    this.SendPropertyChanged("pid");
 58                    this.OnpidChanged();
 59                }
 60            }
 61        }
 62        
 63        [Column(Storage="_poid", DbType="Int NOT NULL")]
 64        [DataMember(Order = 1)]
 65        public int poid
 66        {
 67            get
 68            {
 69                return this._poid;
 70            }
 71            set
 72            {
 73                if ((this._poid != value))
 74                {
 75                    if (this._order.HasLoadedOrAssignedValue)
 76                    {
 77                        throw new System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException();
 78                    }
 79                    this.OnpoidChanging(value);
 80                    this.SendPropertyChanging();
 81                    this._poid = value;
 82                    this.SendPropertyChanged("poid");
 83                    this.OnpoidChanged();
 84                }
 85            }
 86        }
 87        
 88        [Column(Storage="_pName", DbType="VarChar(50) NOT NULL", CanBeNull=false)]
 89        [DataMember(Order = 2)]
 90        public string pName
 91        {
 92            get
 93            {
 94                return this._pName;
 95            }
 96            set
 97            {
 98                if ((this._pName != value))
 99                {
100                    this.OnpNameChanging(value);
101                    this.SendPropertyChanging();
102                    this._pName = value;
103                    this.SendPropertyChanged("pName");
104                    this.OnpNameChanged();
105                }
106            }
107        }
108        
109        [Column(Storage="_price", DbType="Decimal(18,2) NOT NULL")]
110        [DataMember(Order = 3)]
111        public decimal price
112        {
113            get
114            {
115                return this._price;
116            }
117            set
118            {
119                if ((this._price != value))
120                {
121                    this.OnpriceChanging(value);
122                    this.SendPropertyChanging();
123                    this._price = value;
124                    this.SendPropertyChanged("price");
125                    this.OnpriceChanged();
126                }
127            }
128        }
129        
130        [Column(Storage="_pdate", DbType="DateTime NOT NULL")]
131        [DataMember(Order = 4)]
132        public System.DateTime pdate
133        {
134            get
135            {
136                return this._pdate;
137            }
138            set
139            {
140                if ((this._pdate != value))
141                {
142                    this.OnpdateChanging(value);
143                    this.SendPropertyChanging();
144                    this._pdate = value;
145                    this.SendPropertyChanged("pdate");
146                    this.OnpdateChanged();
147                }
148            }
149        }
150        
151        [Association(Name="order_product", Storage="_order", ThisKey="poid", IsForeignKey=true)]
152        [DataMember(Order = 5)]
153        public order order
154        {
155            get
156            {
157                return this._order.Entity;
158            }
159            set
160            {
161                order previousValue = this._order.Entity;
162                if (((previousValue != value) 
163                            || (this._order.HasLoadedOrAssignedValue == false)))
164                {
165                    this.SendPropertyChanging();
166                    if ((previousValue != null))
167                    {
168                        this._order.Entity = null;
169                        previousValue.products.Remove(this);
170                    }
171                    this._order.Entity = value;
172                    if ((value != null))
173                    {
174                        value.products.Add(this);
175                        this._poid = value.oid;
176                    }
177                    else
178                    {
179                        this._poid = default(int);
180                    }
181                    this.SendPropertyChanged("order");
182                }
183            }
184        }
185        
186        public event PropertyChangingEventHandler PropertyChanging;
187        
188        public event PropertyChangedEventHandler PropertyChanged;
189        
190        protected virtual void SendPropertyChanging()
191        {
192            if ((this.PropertyChanging != null))
193            {
194                this.PropertyChanging(this, emptyChangingEventArgs);
195            }
196        }
197        
198        protected virtual void SendPropertyChanged(String propertyName)
199        {
200            if ((this.PropertyChanged != null))
201            {
202                this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
203            }
204        }
205    }

Remarks类：

Code
  1[Table(Name="dbo.REMARK")]
  2    [DataContract(Name = "Remarks", Namespace = "http://www.lgx.OrderLinq")]
  3    public partial class REMARK : INotifyPropertyChanging, INotifyPropertyChanged
  4    {
  5        
  6        private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(String.Empty);
  7        
  8        private int _RID;
  9        
 10        private string _RNAME;
 11        
 12        private int _RCID;
 13        
 14        private string _RCONTENT;
 15        
 16        private System.DateTime _RTIME;
 17        
 18    Extensibility Method Definitions#region Extensibility Method Definitions
 19    partial void OnLoaded();
 20    partial void OnValidate(System.Data.Linq.ChangeAction action);
 21    partial void OnCreated();
 22    partial void OnRIDChanging(int value);
 23    partial void OnRIDChanged();
 24    partial void OnRNAMEChanging(string value);
 25    partial void OnRNAMEChanged();
 26    partial void OnRCIDChanging(int value);
 27    partial void OnRCIDChanged();
 28    partial void OnRCONTENTChanging(string value);
 29    partial void OnRCONTENTChanged();
 30    partial void OnRTIMEChanging(System.DateTime value);
 31    partial void OnRTIMEChanged();
 32    #endregion
 33        
 34        public REMARK()
 35        {
 36            OnCreated();
 37        }
 38        
 39        [Column(Storage="_RID", AutoSync=AutoSync.OnInsert, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
 40        [DataMember(Order=0)]
 41        public int RID
 42        {
 43            get
 44            {
 45                return this._RID;
 46            }
 47            set
 48            {
 49                if ((this._RID != value))
 50                {
 51                    this.OnRIDChanging(value);
 52                    this.SendPropertyChanging();
 53                    this._RID = value;
 54                    this.SendPropertyChanged("RID");
 55                    this.OnRIDChanged();
 56                }
 57            }
 58        }
 59        
 60        [Column(Storage="_RNAME", DbType="VarChar(50) NOT NULL", CanBeNull=false)]
 61        [DataMember(Order = 1)]
 62        public string RNAME
 63        {
 64            get
 65            {
 66                return this._RNAME;
 67            }
 68            set
 69            {
 70                if ((this._RNAME != value))
 71                {
 72                    this.OnRNAMEChanging(value);
 73                    this.SendPropertyChanging();
 74                    this._RNAME = value;
 75                    this.SendPropertyChanged("RNAME");
 76                    this.OnRNAMEChanged();
 77                }
 78            }
 79        }
 80        
 81        [Column(Storage="_RCID", DbType="Int NOT NULL")]
 82        [DataMember(Order = 2)]
 83        public int RCID
 84        {
 85            get
 86            {
 87                return this._RCID;
 88            }
 89            set
 90            {
 91                if ((this._RCID != value))
 92                {
 93                    this.OnRCIDChanging(value);
 94                    this.SendPropertyChanging();
 95                    this._RCID = value;
 96                    this.SendPropertyChanged("RCID");
 97                    this.OnRCIDChanged();
 98                }
 99            }
100        }
101        
102        [Column(Storage="_RCONTENT", DbType="VarChar(200) NOT NULL", CanBeNull=false)]
103        [DataMember(Order = 3)]
104        public string RCONTENT
105        {
106            get
107            {
108                return this._RCONTENT;
109            }
110            set
111            {
112                if ((this._RCONTENT != value))
113                {
114                    this.OnRCONTENTChanging(value);
115                    this.SendPropertyChanging();
116                    this._RCONTENT = value;
117                    this.SendPropertyChanged("RCONTENT");
118                    this.OnRCONTENTChanged();
119                }
120            }
121        }
122        
123        [Column(Storage="_RTIME", DbType="DateTime NOT NULL")]
124        [DataMember(Order = 4)]
125        public System.DateTime RTIME
126        {
127            get
128            {
129                return this._RTIME;
130            }
131            set
132            {
133                if ((this._RTIME != value))
134                {
135                    this.OnRTIMEChanging(value);
136                    this.SendPropertyChanging();
137                    this._RTIME = value;
138                    this.SendPropertyChanged("RTIME");
139                    this.OnRTIMEChanged();
140                }
141            }
142        }
143        
144        public event PropertyChangingEventHandler PropertyChanging;
145        
146        public event PropertyChangedEventHandler PropertyChanged;
147        
148        protected virtual void SendPropertyChanging()
149        {
150            if ((this.PropertyChanging != null))
151            {
152                this.PropertyChanging(this, emptyChangingEventArgs);
153            }
154        }
155        
156        protected virtual void SendPropertyChanged(String propertyName)
157        {
158            if ((this.PropertyChanged != null))
159            {
160                this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
161            }
162        }
163    }

    其次，建立WCF服务

Code
 1[ServiceContract(Name = "IOrderService_Contract", Namespace = "http://www.lgx.OrderService/IOrderService_Contract/", SessionMode = SessionMode.Required)]
 2
 3    public interface IOrderService
 4    {
 5        [OperationContract(Name = "SaveOrder_Contract", Action = "http://www.lgx.OrderService/IOrderService/SaveOrder_Contract/", ReplyAction = "http://www.lgx.OrderService/IOrderService/SaveOrder_ContractResponse")]
 6        [ServiceKnownType(typeof(OrderLinq.product))]
 7        void SaveOrder(OrderLinq.order ord);
 8        [OperationContract(Name = "GetEnt_Contract", Action = "http://www.lgx.OrderService/IOrderService/GetEnt_Contract/", ReplyAction = "http://www.lgx.OrderService/IOrderService/GetEnt_ContractResponse")]
 9        Ent GetEnt();
10        [OperationContract(Name = "GetOrder_Contract", Action = "http://www.lgx.OrderService/IOrderService/GetOrder_Contract/", ReplyAction = "http://www.lgx.OrderService/IOrderService/GetOrder_ContractResponse")]
11        OrderLinq.order GetOrder();
12
13        [OperationContract(Name = "GetProduct_Contract", Action = "http://www.lgx.OrderService/IOrderService/GetProduct_Contract/", ReplyAction = "http://www.lgx.OrderService/IOrderService/GetProduct_ContractResponse")]
14        product GetProduct();
15
16        [OperationContract(Name = "SaveRemak_Contract", Action = "http://www.lgx.OrderService/IOrderService/SaveRemak_Contract/", ReplyAction = "http://www.lgx.OrderService/IOrderService/SaveRemak_ContractResponse")]
17        void SaveRemak(REMARK remark);
18
19    }

 

建立客户端并进行远程引用和调用：

Code
 1static void Main(string[] args)
 2        {
 3            //初始化属性
 4            Remarks remark = new Remarks();
 5            remark.RCID = 1;
 6            remark.RCONTENT = "顶一下";
 7            remark.RNAME = "五哥";
 8            remark.RTIME = DateTime.Now;
 9
10            //初始化属性
11            Orders orders = new Orders();
12            orders.odate = DateTime.Now;
13            orders.totalPrice = Convert.ToDecimal(0.0f);
14           
15
16            OrderService_ContractClient clients = new OrderService_ContractClient();
17            //在这里操作评论表插入数据没有问题
18            clients.SaveRemak_Contract(remark);
19            //插入订单时提示EntitySet<product>为空，因为有主外键关系映射
20            clients.SaveOrder_Contract(orders);
21

 异常

Code
 1
 2//这里提示EntitySet<product>为空，不知为何，
 3//如果数据库表没有主外键映射则不会有这个问题
 4//希望大家帮忙解决，实在是感激不尽呀！！
 5[Association(Name="order_product", Storage="_products", OtherKey="poid")]
 6        [DataMember(Order = 3)]
 7        public EntitySet<product> products
 8        {
 9            get
10            {
11                return this._products;
12            }
13            set
14            {
15                this._products.Assign(value);
16            }
17        }