在 Visual Studio 的 AWS Toolkit 中调用 Alexa Skill 示例请求时出现 JSON 错误

Question

我正在尝试跟随一个 youtube 视频教程，该教程教您如何在 C# 中构建一个简单的 alexa 技能。视频很旧，有些内容已弃用。最近的一位 cmets 说，在 Visual Studio 2019 中，您必须将一行代码更改为 [assembly:LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]

所以现在我的函数看起来像这样：

using System.Net.Http;
using Alexa.NET.Request;
using Alexa.NET.Request.Type;
using Alexa.NET.Response;
using Amazon.Lambda.Core;

// Assembly attribute to enable the Lambda function's JSON input to be converted into a .NET class.
[assembly: LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]
namespace LambdaAlexa
{
    public class Function
    {

        public const string INVOCATION_NAME = "Country Info";

        public SkillResponse FunctionHandler(SkillRequest input, ILambdaContext context)
        {

            var requestType = input.GetRequestType();
            if (requestType == typeof(IntentRequest))
            {
                return MakeSkillResponse(
                        $"Hello Infotec! This is the first response from your Alexa skill using c sharp.",
                        true);
            }
            else
            {
                return MakeSkillResponse(
                        $"I don't know how to handle this intent. Please say something like Alexa, ask {INVOCATION_NAME} about Canada.",
                        true);
            }
        }


        private SkillResponse MakeSkillResponse(string outputSpeech,
            bool shouldEndSession,
            string repromptText = "Just say, tell me about Canada to learn more. To exit, say, exit.")
        {
            var response = new ResponseBody
            {
                ShouldEndSession = shouldEndSession,
                OutputSpeech = new PlainTextOutputSpeech { Text = outputSpeech }
            };

            if (repromptText != null)
            {
                response.Reprompt = new Reprompt() { OutputSpeech = new PlainTextOutputSpeech() { Text = repromptText } };
            }

            var skillResponse = new SkillResponse
            {
                Response = response,
                Version = "1.0"
            };
            return skillResponse;
        }
    }
}

我在上传函数后尝试调用 MyColorIs 示例请求，但由于某种原因我得到了这个响应。

{
  "errorType": "JsonSerializerException",
  "errorMessage": "Error converting the Lambda event JSON payload to type Alexa.NET.Request.SkillRequest: Deserialization of reference types without parameterless constructor is not supported. Type 'Alexa.NET.Request.Type.Request'",
  "stackTrace": [
    "at Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer.Deserialize[T](Stream requestStream)",
    "at lambda_method(Closure , Stream , Stream , LambdaContextInternal )"
  ],
  "cause":   {
    "errorType": "NotSupportedException",
    "errorMessage": "Deserialization of reference types without parameterless constructor is not supported. Type 'Alexa.NET.Request.Type.Request'",
    "stackTrace": [
      "at System.Text.Json.ThrowHelper.ThrowNotSupportedException_DeserializeCreateObjectDelegateIsNull(Type invalidType)",
      "at System.Text.Json.JsonSerializer.HandleStartObject(JsonSerializerOptions options, ReadStack& state)",
      "at System.Text.Json.JsonSerializer.ReadCore(JsonSerializerOptions options, Utf8JsonReader& reader, ReadStack& readStack)",
      "at System.Text.Json.JsonSerializer.ReadCore(Type returnType, JsonSerializerOptions options, Utf8JsonReader& reader)",
      "at System.Text.Json.JsonSerializer.ParseCore(ReadOnlySpan`1 utf8Json, Type returnType, JsonSerializerOptions options)",
      "at System.Text.Json.JsonSerializer.Deserialize[TValue](ReadOnlySpan`1 utf8Json, JsonSerializerOptions options)",
      "at Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer.Deserialize[T](Stream requestStream)"
    ]
  }
}

有人知道这里出了什么问题吗？我已经用谷歌搜索了这个错误，但没有出现大量有用的信息，而且我很困惑。谢谢

Answer 1

通过NuGet安装Amazon.Lambda.Serialization.Json包并替换

[assembly:LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]

与

[assembly: LambdaSerializerAttribute(typeof(Amazon.Lambda.Serialization.Json.JsonSerializer))]