我有一个我定义的Device类，它有2个属性，LocalConnection和Connection，它们具有相同的定义类Connection。
这是Device类：
[ComVisible(true)]
[TypeConverter(typeof(ExpandableObjectConverter))]
public class Device
{
#region Fields
private PacketMutexQueue PacketIn = new PacketMutexQueue(100, 5000);
private PacketMutexQueue PacketOut = new PacketMutexQueue(100, 5000);
private bool wantLocal = false;
private Connection localConnection = new Connection();
private Connection connection = new Connection();
private Thread packetfactorythread;
private Dispatcher dispatcher;
private MutexBindingList<PD_Log> logs = new MutexBindingList<PD_Log>();
protected Packet configuration;
private ConfigurationCache configurationCache;
private Thread sendLogsThread;
private bool fetchingLogs;
#endregion
~Device()
{
if ( Connection != null)
if (Connection.Connected)
Connection.Disconnect();
}
#region Properties
[Browsable (false)]
public virtual long PK { get; set; }
[DescriptionAttribute("Connection Configuration"), DisplayName("Want Local Connection")]
public virtual bool WantLocal
{
get { return wantLocal; }
set { wantLocal = value; }
}
[DescriptionAttribute("Connection Configuration"), DisplayName("Local Connection")]
public virtual Connection LocalConnection
{
get { return localConnection; }
set { localConnection = value; }
}
[DescriptionAttribute("Connection Configuration"), DisplayName("Network Connection")]
public virtual Connection Connection
{
get { return connection; }
set { connection = value; }
}
[Browsable (false)]
public virtual PacketMutexQueue PackQueueIn
{
get { return PacketIn; }
set { PacketIn = value; }
}
[Browsable (false)]
public virtual PacketMutexQueue PackQueueOut
{
get { return PacketOut; }
set { PacketOut = value; }
}
[Browsable (false)]
public virtual Thread PacketFactoryThread
{
get { return packetfactorythread; }
set { packetfactorythread = value; }
}
[Browsable (false)]
public virtual MutexBindingList<PD_Log> Logs
{
get { return logs; }
set { logs = value; }
}
[CategoryAttribute("Configuration"),
DescriptionAttribute("PD Configuration")]
public virtual Packet Configuration
{
get { return configuration; }
set { configuration = value; }
}
[Browsable (false)]
public virtual ConfigurationCache ConfigurationCache
{
get { return configurationCache; }
set { configurationCache = value; }
}
[Browsable (false)]
public virtual Dispatcher Dispatcher
{
get { return dispatcher; }
set { dispatcher = value; }
}
[Browsable (false)]
public virtual Thread SendLogsThread
{
get { return sendLogsThread; }
set { sendLogsThread = value; }
}
[Browsable (false)]
public virtual bool FetchingLogs
{
get { return fetchingLogs; }
set { fetchingLogs = value; }
}
#endregion
}
这是我的连接类：
[TypeConverter(typeof(ExpandableObjectConverter))]
[CategoryAttribute("Connection")]
public class Connection
{
#region Fields
protected byte[] Data = new byte[2048];
protected int size = 2048;
protected StringMutexQueue InBuffer = new StringMutexQueue(100, 5000);
protected StringMutexQueue OutBuffer = new StringMutexQueue(100, 5000);
private bool connected;
#endregion
#region Properties
[Browsable (false)]
public virtual StringMutexQueue BufferIn
{
get { return InBuffer; }
set { InBuffer = value; }
}
[Browsable(false)]
public virtual StringMutexQueue BufferOut
{
get { return OutBuffer; }
set { OutBuffer = value; }
}
[DescriptionAttribute("Connected")]
public virtual bool Connected
{
get { return connected; }
set { connected = value; }
}
[Browsable(false)]
public virtual long PK { get; set; }
#endregion
public virtual void Connect()
{
throw new System.NotImplementedException();
}
public virtual void Disconnect()
{
throw new System.NotImplementedException();
}
public Connection() { }
}
我有两个派生自Connection类，ConnectionTCP和ConnectionSerial的类。
最后，这是我的设备映射：
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class xmlns="urn:nhibernate-mapping-2.2" name="EMTRAC.Devices.Device, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" table="`Device`">
<id name="PK" type="System.Int64, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
<column name="PK" />
<generator class="identity" />
</id>
<many-to-one class="EMTRAC.Connections.Connection, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="LocalConnection" lazy="false" fetch="join" cascade="all">
<column name="LocalConnection_id" />
</many-to-one>
<many-to-one class="EMTRAC.Connections.Connection, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="Connection" lazy="false" fetch="join" cascade="all" unique="true">
<column name="Connection_id" />
</many-to-one>
<many-to-one class="EMTRAC.Packets.Packet, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="Configuration" lazy="false" cascade="all">
<column name="Configuration_id" />
</many-to-one>
<joined-subclass name="EMTRAC.Intersections.Intersection, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
<key>
<column name="Device_id" />
</key>
<bag name="Zones">
<key>
<column name="Intersection_id" />
</key>
<one-to-many class="EMTRAC.Zones.Zone, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"/>
</bag>
<many-to-one class="EMTRAC.Intersections.Streets, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="Streets" lazy="false" cascade="all">
<column name="Streets_id" />
</many-to-one>
<many-to-one class="EMTRAC.Positions.Position, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="Position" cascade="all">
<column name="Position" />
</many-to-one>
</joined-subclass>
<joined-subclass name="EMTRAC.Vehicles.Vehicle, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
<key>
<column name="Device_id" />
</key>
<property name="Active" type="System.Boolean, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
<column name="Active" />
</property>
<property name="Status" type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
<column name="Status" />
</property>
<property name="Velocity" type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
<column name="Velocity" />
</property>
<property name="Heading" type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
<column name="Heading" />
</property>
<many-to-one class="EMTRAC.Positions.Position, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="Position" lazy="false" cascade="all">
<column name="Position_id" />
</many-to-one>
<many-to-one class="EMTRAC.VehicleClasses.VehicleClass, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="VehClass" lazy="false" cascade="all">
<column name="VehClass_id" />
</many-to-one>
</joined-subclass>
Intersection类派生自Device基类。
我的问题是我可以将交叉点保存到数据库中，并且所有内容都可以正确映射。但是，保存交叉点并尝试使用NHibernate加载对象后使用：
IQuery q = session.CreateQuery("from Device");
IList results = q.List();
我收到以下例外情况：
“无法加载实体：[EMTRAC.Connections.Connection＃1] [SQL：SELECT connection0_.PK as PK30_0_，connection0_ .Connected as Connected30_0_，connection0_1_.Baud as Baud31_0_，connection0_1_.Port as Port31_0_，connection0_2_.EndPoint作为EndPoint32_0_，connection0_2_.Port作为Port32_0_，例如当connection0_1_.Connection_id不为null时，则当connection0_2_.Connection_id不为null时为1，当connection0_.PK不为null时为2然后0结束为clazz_0_ FROM [Connection] connection0_ left outer join ConnectionSerial connection0_1_ on connection0_.PK = connection0_1_.Connection_id left outer join ConnectionTCP connection0_2_ on connection0_.PK = connection0_2_.Connection_id WHERE connection0_.PK =？]“
内部例外：
{“对象引用未设置为对象的实例。”}
我的设备表有一个PK列，后面是LocalConnectionId和ConnectionId的列，以及一个配置列。 LocalConnectionId和ConnectionId列中的ID正确映射到Connection表，而后者又映射到相应的派生类ConnectionTCP或ConnectionSerial，并且所有内容似乎都应该正常工作。
保存对象时没有收到任何错误。
我在配置中启用了showsql并复制了用于将对象加载到我的SQL Management Studio中的sql语句，并且select语句执行得很好：
declare @p0 BIGINT
SET @p0 = 1
NHibernate:
SELECT
connection0_.PK as PK30_0_,
connection0_.Connected as Connected30_0_,
connection0_1_.Baud as Baud31_0_,
connection0_1_.Port as Port31_0_,
connection0_2_.EndPoint as EndPoint32_0_,
connection0_2_.Port as Port32_0_,
case
when connection0_1_.Connection_id is not null then 1
when connection0_2_.Connection_id is not null then 2
when connection0_.PK is not null then 0
end
as clazz_0_
FROM
[Connection] connection0_ left outer join ConnectionSerial connection0_1_
on
connection0_.PK=connection0_1_.Connection_id left outer join ConnectionTCP connection0_2_
on
connection0_.PK=connection0_2_.Connection_id
WHERE connection0_.PK=@p0
唯一奇怪的是我的EndPoint和Port是NULL，但这只是因为我还没有为对象设置这些值。
任何想法我做错了什么？
提前致谢。
[编辑] 这里要求的是ConnectionTCP和ConnectionSerial类：
[TypeConverter(typeof(ExpandableObjectConverter))]
public class ConnectionTCP : Connection
{
#region Fields
private TcpClient client;
protected NetworkStream stream;
private string endpoint;
private int port;
private int maxMessageSize = 4096;
Thread commThread;
#endregion
#region Constructors
public ConnectionTCP() { }
public ConnectionTCP(string ipAdd, int port)
{
// Set the Device EndPoint
EndPoint = ipAdd;
// Set the Device Port
Port = port;
Client = new TcpClient(EndPoint, Port);
// Set Connected status
Connected = false;
}
#endregion
#region Properties
[Browsable(false)]
public virtual long PK { get; set; }
[Browsable(false)]
public virtual TcpClient Client
{
get { return client; }
set { client = value; }
}
[Browsable(false)]
public virtual NetworkStream Stream
{
get { return stream; }
set { stream = value; }
}
[CategoryAttribute("Network Address"),
DisplayName("End Point"),
DescriptionAttribute("The network address of the Priority Detector.")]
public virtual string EndPoint
{
get { return endpoint; }
set { endpoint = value; }
}
[CategoryAttribute("Port"),
DescriptionAttribute("The port used to connect to the Priority Detector.")]
public virtual int Port
{
get { return port; }
set { port = value; }
}
#endregion
}
[TypeConverter(typeof(ExpandableObjectConverter))]
public class ConnectionSerial : Connection
{
private Thread commThread;
private int dataBits = 8;
private Parity parity = Parity.None;
private List<string> ports = new List<string>();
private SerialPort serialConn;
private StopBits stopBits = StopBits.One;
private int timeoutRead = 10000;
private int timeoutWrite = 10000;
private int baud;
private string port;
[Browsable (false)]
public virtual long PK { get; set; }
[DescriptionAttribute("Serial Connection"), DisplayName("Serial Connection")]
public virtual SerialPort SerialConn
{
get { return serialConn; }
set { serialConn = value; }
}
[Browsable (false)]
public virtual int Baud
{
get { return SerialConn.BaudRate; }
set { baud = SerialConn.BaudRate; }
}
[Browsable(false)]
public virtual string Port
{
get { return SerialConn.PortName; }
set { port = SerialConn.PortName; }
}
#region Constructors
public ConnectionSerial() { }
public ConnectionSerial(string port, int baud)
{
SerialConn = new SerialPort();
SerialConn.PortName = port;
SerialConn.BaudRate = baud;
SerialConn.Parity = parity;
SerialConn.DataBits = dataBits;
SerialConn.StopBits = stopBits;
SerialConn.ReadTimeout = timeoutRead;
SerialConn.WriteTimeout = timeoutWrite;
// Set Connected status
Connected = false;
}
#endregion
}
这是Connections的映射：
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"> <class xmlns="urn:nhibernate-mapping-2.2" name="EMTRAC.Connections.Connection, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" table="`Connection`"> <id name="PK" type="System.Int64, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="PK" /> <generator class="identity" /> </id> <property name="Connected" type="System.Boolean, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Connected" /> </property> <joined-subclass name="EMTRAC.Connections.ConnectionSerial, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"> <key> <column name="Connection_id" /> </key> <property name="Baud" type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Baud" /> </property> <property name="Port" type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Port" /> </property> </joined-subclass> <joined-subclass name="EMTRAC.Connections.ConnectionTCP, EMTRAC_v3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"> <key> <column name="Connection_id" /> </key> <property name="EndPoint" type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="EndPoint" /> </property> <property name="Port" type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Port" /> </property> <!--<property name="Client" type="EMTRAC.Connections.TcpClientMapper, EMTRAC_v3"/>--> <!--<property name="Client" type="EMTRAC.Connections.TcpClientMapper, EMTRAC_v3" />--> </joined-subclass>
答案 0 :(得分：1)
NHibernate正在尝试从数据库加载ConnectionSerial对象。当它尝试设置Baud和Port属性的值时，会抛出NullReferenceException，因为SerialConn还没有值。