附加信息:将值[string]转换为类型[enum]时出错

Question

每当我试图反序列化下面的json字符串时，我都会收到这个错误：

错误：

附加信息：转换值时出错"invalid_request_error"以键入"ErrorType"。路径"type"，第2行，位置33。

Json字符串

{
  "error": {
    "type": "invalid_request_error",
    "message": "Invalid request (check that your POST content type is application/x-www-form-urlencoded). If you have any questions, we can help at https://support.stripe.com/."
  }
}  

代码

private void btnDeserialize_Click(object sender, EventArgs e)
{
    var r = Components.JsonMapper.MapFromJson<Components.DTO.Error>(txtToDeserialize.Text, "error");
    txtDeserialized.Text = JsonConvert.SerializeObject(r);
}  

JsonMapper

public static class JsonMapper
{
    public static T MapFromJson<T>(string json, string parentToken = null)
    {
        var jsonToParse = string.IsNullOrEmpty(parentToken) ? json : JObject.Parse(json).SelectToken(parentToken).ToString();
        return JsonConvert.DeserializeObject<T>(jsonToParse);
    }
}  

枚举

public enum ErrorCode
{
    Default,
    [JsonProperty("invalid_number")]
    InvalidNumber,
    [JsonProperty("invalid_expiry_month")]
    InvalidExpiryMonth,
    [JsonProperty("invalid_expiry_year")]
    InvalidExpiryYear,
    [JsonProperty("invalid_cvc")]
    InvalidCvc,
    [JsonProperty("incorrect_number")]
    IncorrectNumber,
    [JsonProperty("expired_card")]
    ExpiredCard,
    [JsonProperty("incorrect_cvc")]
    IncorrectCvc,
    [JsonProperty("incorrect_zip")]
    IncorrectZip,
    [JsonProperty("card_declined")]
    CardDeclined,
    [JsonProperty("missing")]
    Missing,
    [JsonProperty("processing_error")]
    ProcessingError
}
public enum ErrorType
{
    Default,
    [JsonProperty("api_connection_error")]
    ApiConnectionError,
    [JsonProperty("api_error")]
    ApiError,
    [JsonProperty("authentication_error")]
    AuthenticationError,
    [JsonProperty("card_error")]
    CardError,
    [JsonProperty("invalid_request_error")]
    InvalidRequestError,
    [JsonProperty("rate_limit_error")]
    RateLimitError
}

我想坚持使用枚举而不是字符串
解决这个问题的好办法是什么？

Answer 1

您有几个问题：

1. 您需要使用StringEnumConverter将枚举序列化为字符串。

2. 您需要使用[EnumMember(Value = "enum_name")]而不是[JsonProperty("enum_name")]来指定重新映射的枚举名称。为了与数据协定序列化程序完全兼容，您可能还希望添加[DataContract]。

3. 一旦您将JSON字符串解析为JToken，使用JToken.ToObject()或JToken.CreateReader()对其进行反序列化将更加高效。无需序列化为字符串，然后从头开始重新解析。

因此，你的类型应该看起来像：

[DataContract]
public enum ErrorCode
{
    Default,
    [EnumMember(Value = "invalid_number")]
    InvalidNumber,
    [EnumMember(Value = "invalid_expiry_month")]
    InvalidExpiryMonth,
    [JsonProperty("invalid_expiry_year")]
    InvalidExpiryYear,
    [EnumMember(Value = "invalid_cvc")]
    InvalidCvc,
    [EnumMember(Value = "incorrect_number")]
    IncorrectNumber,
    [EnumMember(Value = "expired_card")]
    ExpiredCard,
    [EnumMember(Value = "incorrect_cvc")]
    IncorrectCvc,
    [EnumMember(Value = "incorrect_zip")]
    IncorrectZip,
    [EnumMember(Value = "card_declined")]
    CardDeclined,
    [EnumMember(Value = "missing")]
    Missing,
    [EnumMember(Value = "processing_error")]
    ProcessingError
}
public class Error
{
    public ErrorType type { get; set; }
    public string message { get; set; }
}
[DataContract]
public enum ErrorType
{
    Default,
    [EnumMember(Value = "api_connection_error")]
    ApiConnectionError,
    [EnumMember(Value = "api_error")]
    ApiError,
    [EnumMember(Value = "authentication_error")]
    AuthenticationError,
    [EnumMember(Value = "card_error")]
    CardError,
    [EnumMember(Value = "invalid_request_error")]
    InvalidRequestError,
    [EnumMember(Value = "rate_limit_error")]
    RateLimitError
}

以及您的映射器：

public static class JsonMapper
{
    private static JsonReader CreateReader(string json, string parentToken)
    {
        if (string.IsNullOrEmpty(parentToken))
            return new JsonTextReader(new StringReader(json));
        else
        {
            var token = JToken.Parse(json).SelectToken(parentToken);
            return token == null ? null : token.CreateReader();
        }
    }
    public static T MapFromJson<T>(string json, string parentToken = null)
    {
        var settings = new JsonSerializerSettings { Converters = new [] { new StringEnumConverter() } };
        using (var reader = CreateReader(json, parentToken))
        {
            if (reader == null)
                return default(T);
            return JsonSerializer.CreateDefault(settings).Deserialize<T>(reader);
        }
    }
}