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c# - C#AutoMapperMappingException KeyNotFoundException

我猜所有的信息，除了例外是额外的，几乎没有关系（这里是为了完整性）。问题是：根据下面的异常，到底遇到了什么问题？
我无法理解异常消息。据我所知，存在一个将BsonDocument映射到ChildItemViewModel的错误。Id、Description和SequentialOrgId已成功映射…然后发生了一些事情，尽管这些是唯一的属性。似乎它在寻找_id（正在转换为childitemviewmodel的bsondocument）中的cI（一个不存在的属性），但我不知道这是否正确，因为这没有意义。
这是一段代码（映射），我相信会发生这种情况，但我不知道，因为我没有行号。

        foreach (BsonDocument cI in childItems)
        {
            ChildItemViewModel childItem = Mapper.Map<BsonDocument, ChildItemViewModel>(cI);
            itemView.ChildItems.Add(childItem);
        }

这是实体框架视图模型（类）：
public class ChildItemViewModel
{
    public long Id { get; set; }
    public string Description { get; set; }
    public long SequentialOrgId { get; set; }
}

这是消息来源：
c# - C#AutoMapperMappingException KeyNotFoundException-LMLPHP
编辑：我已经确认childitems字段是问题的根源。如果我用下面的代码清除它们，问题就会消失：
db.items.update(
   { _id: 1245846 },
   { $set:
      {
            "ChildItems":[],
            "ChildItemsAmount": NumberInt(0)
      }
   }
)

例外情况：
 {"message":"AutoMapper.AutoMapperMappingException:

 Mapping types:
 BsonDocument -> Int64
 MongoDB.Bson.BsonDocument -> System.Int64

 Destination path:
 ChildItemViewModel.Id.Id

 Source value:
 { \"Id\" : NumberLong(1245854), \"Description\" : \"Image of Ext USB drive containing backup files labeled \\\"Kevin SomeLastName Backups\\\"\", \"SequentialOrgId\" : NumberLong(189) } ---> System.Collections.Generic.KeyNotFoundException: Element '_id' not found.
    at MongoDB.Bson.BsonDocument.get_Item(String name)
    at lambda_method(Closure , BsonDocument )
    at AutoMapper.Internal.DelegateBasedResolver`2.Resolve(ResolutionResult source)
    at AutoMapper.NullReferenceExceptionSwallowingResolver.Resolve(ResolutionResult source)
    at System.Linq.Enumerable.Aggregate[TSource,TAccumulate](IEnumerable`1 source, TAccumulate seed, Func`3 func)
    at AutoMapper.Mappers.TypeMapObjectMapperRegistry.PropertyMapMappingStrategy.MapPropertyValue(ResolutionContext context, IMappingEngineRunner mapper, Object mappedObject, PropertyMap propertyMap)
    --- End of inner exception stack trace ---
    at AutoMapper.Mappers.TypeMapObjectMapperRegistry.PropertyMapMappingStrategy.MapPropertyValue(ResolutionContext context, IMappingEngineRunner mapper, Object mappedObject, PropertyMap propertyMap)
    at AutoMapper.Mappers.TypeMapObjectMapperRegistry.PropertyMapMappingStrategy.Map(ResolutionContext context, IMappingEngineRunner mapper)
    at AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map(ResolutionContext context)
    at AutoMapper.MappingEngine.Map[TSource,TDestination](TSource source)
    at API.Classes.Automapper.ItemViewModelConverter.Convert(ResolutionContext resolution)
    at AutoMapper.Internal.MappingExpression`2.<>c__DisplayClass51_0.<ConvertUsing>b__0(ResolutionContext context)
    at AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map(ResolutionContext context)
    at AutoMapper.MappingEngine.Map[TSource,TDestination](TSource source)
    at MongoDB.Bson.Serialization.Serializers.ProjectingDeserializer`2.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
    at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
    at MongoDB.Driver.Core.WireProtocol.Messages.Encoders.BinaryEncoders.ReplyMessageBinaryEncoder`1.ReadMessage()
    at MongoDB.Driver.Core.Connections.BinaryConnection.<ReceiveMessageAsync>d__15.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at MongoDB.Driver.Core.WireProtocol.QueryWireProtocol`1.<ExecuteAsync>d__0.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at MongoDB.Driver.Core.Servers.ClusterableServer.ServerChannel.<ExecuteProtocolAsync>d__24`1.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at MongoDB.Driver.Core.Operations.FindOperation`1.<ExecuteAsync>d__2.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at MongoDB.Driver.OperationExecutor.<ExecuteReadOperationAsync>d__0`1.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at MongoDB.Driver.MongoCollectionImpl`1.<ExecuteReadOperation>d__35`1.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at MongoDB.Driver.IFindFluentExtensions.<SingleOrDefaultAsync>d__f`2.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at API.Controllers.ItemsController.<GetItem>d__2.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Threading.Tasks.TaskHelpersExtensions.<CastToObject>d__3`1.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Controllers.AuthenticationFilterResult.<ExecuteAsync>d__0.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
    at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()"}

最佳答案

MongoDB驱动程序本身就是罪魁祸首。当遇到id属性时，它会自动假设需要将其映射到相应的_id字段。为了解决问题，您只需添加一个属性，告诉驱动程序您比它更了解：

public class ChildItemViewModel
{
    [BsonElement("Id")]
    public long Id { get; set; }
    public string Description { get; set; }
    public long SequentialOrgId { get; set; }
}

另外，似乎还有[BsonNoId]属性，您可以在类级别应用该属性：
[BsonNoId]
public class ChildItemViewModel

10-08 17:57
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