Newtonsoft.Json.JsonSerializationException：无法创建类型（抽象类）的实例

Question

我想为下面的示例测试序列化，但我最终得到此错误Newtonsoft.Json.JsonSerializationException : Could not create an instance of type Core.Model.Assets.Asset. Type is an interface or abstract class and cannot be instantiated. Path '_source.articleAssets[0].asset.refId'。在以下示例中，Asset是一个抽象类，有超过5派生类（例如：BrightcoveVideo是派生类中的一个）

ArticleAssets = new List<ArticleAsset>() 
{ 
    new ArticleAsset() 
    { 
     ArticleId = 1, 
     Asset = new BrightcoveVideo() 
     { 
      AssetType = AssetTypeEnum.BrightcoveTitle, Id = 11, Name = "something for a name", DisplayName = "some display", RefId = "refrefref" 
     }, 
     AssetId = 11, 
     AssetType = AssetTypeEnum.BrightcoveTitle 
    } 
} 

我有一个自定义JsonConverter类看起来像这样：

public class AssetTypeConverter : JsonConverter 
{ 
    public override bool CanConvert(Type objectType) 
    { 
     return objectType == typeof(Asset) || objectType == typeof(SearchResultAsset); 
    } 

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) 
    { 
     if (value != null && value.GetType() == typeof(SearchResultAsset)) 
     { 
      throw new NotImplementedException("WriteJson unexpectedly called for SearchResultAsset in AssetTypeConverter"); 
     } 

     throw new NotImplementedException("WriteJson unexpectedly called for Asset in AssetTypeConverter"); 
    } 

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) 
    { 
     if (reader.TokenType == JsonToken.Null) 
     { 
      return null; 
     } 

     Asset concreteAsset = new SearchResultAsset(); 
     serializer.Populate(reader, concreteAsset); 

     return concreteAsset; 
    } 
} 

在ElasticSearchRegistry类，我在下面的方法添加该转换器：

var connectionSettings = new ConnectionSettings(connectionUri); 
_elasticClient = new ElasticClient(connectionSettings); 
connectionSettings.SetJsonSerializerSettingsModifier(p => p.Converters.Add(new AssetTypeConverter())); 

我得到的JsonSerialization除离子在Get请求：

public IGetResponse<Article> GetArticleResponse(int id) 
{ 
    var response = _elasticClient.Get<Article>(i => i.Index(_indexName) 
      .Type(DocumentType) 
      .Id(id) 
     ); 

    return response; 
} 

Answer 1

我知道它是固定的，这是一个非常小的错误。我已经设置JsonSerializerSettings实例ElasticClient这样前：

connectionSettings = new ConnectionSettings(connectionUri); 
connectionSettings.SetJsonSerializerSettingsMo‌​difier(
    p => p.Converters.Add(new AssetTypeConverter()) 
); 
_elasticClient = new ElasticClient(connectionSettings);