2

我得到一个未设置为对象实例的对象引用。：OperatorAssembly: 0 line 157。我不明白什么会触发这个异常

LogFile.Info("order="+order.Id);

if (order.Location != null)
{
    LogFile.Info("order=" + order.Location.Address);
}    
else
{
    LogFile.Info("order location is null");
}

LogFile.Info("order=" + order.Location.Latitude);
LogFile.Info("order=" +  order.IsResolved);
LogFile.Info("order user id=" + order.User.Id);
LogFile.Info("order ser name=" + order.User.Name);
LogFile.Info("order ser dest =" + order.Destination.Address);                       

line 157:
result = new OrderDataDriver
{
    OrderId = order.Id,
    Address = order.Location.Address,
    Lat = order.Location.Latitude,
    Lng = order.Location.Longitude,
    DestinationAddress = order.Destination.Address,
    DestinationLat = order.Destination.Latitude,
    DestinationLng = order.Destination.Longitude,
    IsCanceled = order.IsCanceled,
    IsPendingResponse = order.IsPendingResponse,
    IsResolved = order.IsResolved,
    UserId = order.User.Id,
    Message = order.MessageForDriver,
    UserName = order.User.Name,
    // IsAdvanceBooking = order.AdvenceBookingTime != null,
    AdvanceBookingTime = order.AdvenceBookingTime,
    AdvancePrice = order.CalculatedPrice,
    AdvanceDistance = order.CalculatedDistance,
    SecondsToRespond = 30,
    Status=order.DriverStatus
};

[DataContract]
public class OrderDataDriver
{

    [DataMember] public string Address { get; set; }
    [DataMember] public string Feedback { get; set; }
    [DataMember] public double Lat { get; set; }
    [DataMember] public double Lng { get; set; }
    [DataMember] public int UserId { get; set; }
    [DataMember] public string Status { get; set; }
    [DataMember] public bool? IsEligible { get; set; }
    [DataMember] public bool? IsCanceled { get; set; }
    [DataMember] public bool? IsResolved { get; set; }
    [DataMember] public bool? IsPendingResponse { get; set; }
    [DataMember] public bool? AllowsTracking { get; set; }
    [DataMember]
    public int OrderId { get; set; }
    [DataMember]


    public int App { get; set; }
    [DataMember]
    public int? PreferedDriver { get; set; }
    [DataMember]
    public bool IsAdvanceBooking { get; set; }
    [DataMember]
    public DateTime? AdvanceBookingTime { get; set; }
    [DataMember]
    public double? AdvancePrice { get; set; }
    [DataMember]
    public double? AdvanceDistance { get; set; }
    [DataMember]
    public string DestinationAddress { get; set; }
    [DataMember]
    public double DestinationLat { get; set; }
    [DataMember]
    public double DestinationLng { get; set; }
    [DataMember]
    public string Message { get; set; }
    [DataMember]
    public string UserName { get; set; }
    [DataMember]
    public int SecondsToRespond { get; set; }
}
4

4 回答 4

4

将复杂对象初始化更改为如下所示： 

var result = new OrderDataDriver();
result.blablah = foor.bar;

然后，您将收到一条更好的错误消息，其中包含您尝试访问空对象的属性的确切行号。

这里是参考这个可爱模式的好地方，它使开发人员的生活更轻松 http://en.wikipedia.org/wiki/Fail-fast

于 2013-01-21T21:41:14.930 回答
0

如果属性为 null，则这些访问器中的任何一个都可能崩溃：

//If Location is null BOOM!!!
Lat = order.Location.Latitude,
Lng = order.Location.Longitude,

//If Destination is null BOOM!!!
DestinationAddress = order.Destination.Address,
DestinationLat = order.Destination.Latitude,
DestinationLng = order.Destination.Longitude,
于 2013-01-21T21:39:24.160 回答
0

当您使用对象初始化程序时，例如

result = new OrderDataDriver { OrderId = order.Id, Address = order.Location.Address, Lat = order.Location.Latitude, Lng = order.Location.Longitude, };

不要指望行号（和列号，如果有的话）准确指出大括号内的哪些“属性分配”{ }会导致异常。毕竟，这被转换为对临时（不可见）变量属性的赋值。只有一切顺利，临时变量才会复制到您的result值。

对于涉及对象初始化程序的堆栈跟踪，我也遇到过这种不便。

于 2013-01-21T22:25:18.390 回答
0

由于可能null已经记录了一些事情，因此应该更早地抓住它们。

除非你有一个有副作用的属性获取器。那些是纯粹的邪恶，所以要小心。另一种可能性是另一个线程更改了一个值。这更难证明。

于 2013-01-21T21:44:58.323 回答