Question

我正在使用ASP.NET MVC 5 Web Api。

我现在有很多api的应用程序。最近我实现了自定义JsonConverter，它将根据时区转换日期。

public class CustomInfoConverter : JsonConverter
{

    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(CustomType);
    }
    public override bool CanRead
    {
        get
        {
            return false;
        }
    }
    public override bool CanWrite
    {
        get
        {
            return true;
        }
    }
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var customType = (CustomType)value;
        if (customType == null || null== customType.TimeZone) return;
        //DateTime currentDateTime = customType.Date??DateTime.Now;
        DateTime currentDateTime = DateTime.SpecifyKind(customType.Date ?? DateTime.Now, DateTimeKind.Unspecified);

        DateTime userDateTime = TimeZoneInfo.ConvertTimeFromUtc(currentDateTime, customType.TimeZone);
        customType.Date = userDateTime;
        JsonSerializer innerSerializer = new JsonSerializer();
        foreach (var converter in serializer.Converters.Where(c => !(c is CustomInfoConverter)))
        {
            innerSerializer.Converters.Add(converter);
        }
        innerSerializer.Serialize(writer, customType);


    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }


}

实现这个自定义JsonConverter之后，所有api都在工作，除了一个api，它抛出异常

{＆＃34;消息＆＃34;：＆＃34;发生了错误。＆＃34;，＆＃34; ExceptionMessage＆＃34;：＆＃34; The ＆＃39; ObjectContent`1＆＃39;类型无法序列化响应正文内容类型＆＃39; application / json; 字符集= UTF-8＆＃39;＆＃34;＆＃34; ExceptionType＆＃34;：＆＃34; System.InvalidOperationException＆＃34;＆＃34;堆栈跟踪＆＃34;：空，＆＃34;的InnerException＆＃34; {＆＃34;消息＆＃34;：＆＃34;安错误已经发生。＆＃34;，＆＃34; ExceptionMessage＆＃34;：＆＃34; Token PropertyName in state 属性将导致无效的JSON对象。路径＆＃39; Data.Forms [0]＆＃39;＆＃34;＆＃34; ExceptionType＆＃34;：＆＃34; Newtonsoft.Json.JsonWriterException＆＃34;＆＃34;堆栈跟踪＆＃34; ：＆＃34; 在Newtonsoft.Json.JsonWriter.AutoComplete（JsonToken tokenBeingWritten）\ r \ n at Newtonsoft.Json.JsonWriter.InternalWritePropertyName（String name）\ r \ n at Newtonsoft.Json.JsonTextWriter.WritePropertyName（String name，布尔转义）\ r \ n at Newtonsoft.Json.Serialization.JsonProperty.WritePropertyName（JsonWriter 作家）\ r \ n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject（JsonWriter writer，Object value，JsonObjectContract契约，JsonProperty 成员，JsonContainerContract collectionContract，JsonProperty containerProperty）\ r \ n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue（JsonWriter writer，Object value，JsonContract valueContract，JsonProperty成员， JsonContainerContract containerContract，JsonProperty containerProperty）\ r \ n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList（JsonWriter writer，IEnumerable值，JsonArrayContract契约，JsonProperty 成员，JsonContainerContract collectionContract，JsonProperty containerProperty）\ r \ n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue（JsonWriter writer，Object value，JsonContract valueContract，JsonProperty成员， JsonContainerContract containerContract，JsonProperty containerProperty）\ r \ n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject（JsonWriter writer，Object value，JsonObjectContract契约，JsonProperty 成员，JsonContainerContract collectionContract，JsonProperty containerProperty）\ r \ n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue（JsonWriter writer，Object value，JsonContract valueContract，JsonProperty成员， JsonContainerContract containerContract，JsonProperty containerProperty）\ r \ n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject（JsonWriter writer，Object value，JsonObjectContract契约，JsonProperty 成员，JsonContainerContract collectionContract，JsonProperty containerProperty）\ r \ n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue（JsonWriter writer，Object value，JsonContract valueContract，JsonProperty成员， JsonContainerContract containerContract，JsonProperty containerProperty）\ r \ n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize（JsonWriter jsonWriter，Object value，Type objectType）\ r \ n at Newtonsoft.Json.JsonSerializer.SerializeInternal（JsonWriter jsonWriter，Object value，Type objectType）\ r \ n at Newtonsoft.Json.JsonSerializer.Serialize（JsonWriter jsonWriter，Object 价值）\ r \ n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream（类型 type，Object value，Stream writeStream，Encoding 有效编码）\ r \ n at System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream（类型 type，Object value，Stream writeStream，Encoding 有效编码）\ r \ n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream（类型 type，Object value，Stream writeStream，HttpContent content）\ r \ n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync（类型 type，Object value，Stream writeStream，HttpContent内容， TransportContext transportContext，CancellationToken cancellationToken）\ r \ n ---从前一个位置开始的堆栈跟踪结束抛出异常的地方--- \ r \ n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess（任务任务）\ r \ n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification（任务任务）\ r \ n at System.Runtime.CompilerServices.TaskAwaiter.GetResult（）\ r \ n at System.Web.Http.WebHost.HttpControllerHandler.d__1b.MoveNext（）＆＃34;}}

您可以参考此link了解详情。

Answer 1

问题似乎是，在某些情况下，您从WriteJson()返回而没有写任何内容，特别是在customType.TimeZone == null时：

    var customType = (CustomType)value;
    if (customType == null || null== customType.TimeZone) return;

这样做会导致JSON对象无效，因为调用者已经编写了 name 属性，导致：

{
    "customType":
}

尝试执行此操作会导致您看到异常。

相反，您需要阻止属性本身被序列化。但是，在转换器中这是不可能的，它需要在包含类型中完成。

为避免序列化具有空值的属性，您应在serializer settings中或在属性本身上设置NullValueHandling = NullValueHandling.Ignore：

public class ContainerClass
{
    [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
    public CustomType CustomType { get; set; }
}

要防止在TimeZone属性为空时序列化您的属性，您应该使用conditional property serialization方法向包含类型添加ShouldSerializeXXX()方法，其中XXX与您的属性完全匹配财产名称：

public class ContainerClass
{
    public CustomType CustomType { get; set; }

    public bool ShouldSerializeCustomType()
    {
        return CustomType != null && CustomType.TimeZone != null;
    }
}

Web API：无法序列化内容类型

1 个答案: