ServiceStack：当属性为空时获取 FileNotFoundException？

Question

我正在使用 ServiceStack 并发现了一些奇怪的东西。当 WS Dto 包含一些 null 值时，我在 System.Numerics.Vectors 上得到 FileNotFoundException。例如，我有一个名为“GetBookingSolutions”的 Dto，如下所示：

    [Route(BookingWizard.BASE_PATH + "getbookingsolution", Verbs = "POST", Summary = "Sends booking spec to request server to create/plan the booking")]
public class GetBookingSolution : IReturn<GetBookingSolutionResponse>
{
    public DateTime TimeWanted { get; set; }
    public uint AddressFrom { get; set; }
    // ...
    public Dictionary<uint, int> Equipment { get; set; }
    public Dictionary<uint, int> CoTravellers { get; set; }
}

最后两个是字典，因此是可以为空的对象。如果发送客户端发送如下所示的 JSON：

{
  "TimeWanted": "2018-12-10T09:05:00.000Z",
  "AddressFrom": 14427162,
  "CoTravellers": null,
  "Equipment": null
}

然后我得到异常，如下所示。服务实现永远不会执行，因此代码永远不会到达。相反，我在UncaughtExceptionHandlers 中得到了异常。

如果 JSON 看起来像这样：

{
  "TimeWanted": "2018-12-10T09:05:00.000Z",
  "AddressFrom": 14427162,
}

或者如果字典被填充：

{
  "TimeWanted": "2018-12-10T09:05:00.000Z",
  "AddressFrom": 14427162,
  "CoTravellers": {
    "13486513": 2,
    "13486515": 1
   },
  "Equipment": {
   "13424459": 2,
  }
}

那么错误不会出现。为什么会这样？这是一个错误还是这里有什么建议？ null 值适用于这些属性（如果最终用户未设置它们）。

System.IO.FileNotFoundException: Could not load file or assembly 'System.Numerics.Vectors, Version=4.1.3.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.
File name: 'System.Numerics.Vectors, Version=4.1.3.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
   at System.SpanHelpers.SequenceEqual(Byte& first, Byte& second, NUInt length)
   at System.MemoryExtensions.Equals(ReadOnlySpan`1 span, ReadOnlySpan`1 other, StringComparison comparisonType)
   at ServiceStack.Text.Json.JsonTypeSerializer.EatValue(ReadOnlySpan`1 value, Int32& i)
   at ServiceStack.Text.Common.DeserializeTypeRefJson.StringToType(ReadOnlySpan`1 strType, TypeConfig typeConfig, EmptyCtorDelegate ctorFn, KeyValuePair`2[] typeAccessors)
   at ServiceStack.Text.Common.DeserializeType`1.StringToTypeContext.DeserializeJson(ReadOnlySpan`1 value)
   at ServiceStack.Text.Json.JsonReader.<>c__DisplayClass3_0.<GetParseSpanFn>b__0(ReadOnlySpan`1 v)
   at ServiceStack.Text.JsonSerializer.DeserializeFromSpan(Type type, ReadOnlySpan`1 value)
   at ServiceStack.Text.DefaultMemory.Deserialize(MemoryStream ms, Boolean fromPool, Type type, DeserializeStringSpanDelegate deserializer)
   at ServiceStack.Text.DefaultMemory.<DeserializeAsync>d__34.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 ServiceStack.Host.RestHandler.<CreateRequestAsync>d__16.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 ServiceStack.Host.RestHandler.<CreateRequestAsync>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 ServiceStack.Host.RestHandler.<ProcessRequestAsync>d__14.MoveNext()

Answer 1

这是一个运行时依赖问题，与 DTO 中的 null 无关，这正是触发代码路径需要 System.Numerics.Vectors 依赖的原因，它无法加载.在这种情况下调用System.MemoryExtensions.Equals() 扩展方法。

似乎有一个带有此异常的few issues，看起来this GitHub Thread 有一些您可以尝试的解决方法。