问题描述
我在尝试使用Json.net使用接口值反序列化一个非常复杂的嵌套字典类型时遇到问题.代码位于此处" https://dotnetfiddle.net/JSoAug ",所涉及的类型为:
I am having a problem trying to deserialize a pretty complex nested dictionary type with interface values using Json.net. The code is located here "https://dotnetfiddle.net/JSoAug", and the types in question are:
public class TypeConverter<T, TSerialized> : CustomCreationConverter<T>
where TSerialized : T, new()
{
public override T Create(Type objectType)
{
return new TSerialized();
}
}
public interface IValue
{
Dictionary<string, IValue> SomeValues { get; set; }
}
public class Value : IValue
{
[JsonProperty(ItemConverterType = typeof(TypeConverter<IValue, Value>))]
public Dictionary<string, IValue> SomeValues { get; set; }
}
public interface ISomeAtrributes
{
Dictionary<string, object> Attributes { get; set; }
}
public interface IDataItem : ISomeAtrributes
{
IValue Value { get; set; }
}
public class DataItem : IDataItem
{
[JsonProperty(ItemConverterType = typeof(TypeConverter<IValue, Value>))]
public IValue Value { get; set; }
public Dictionary<string, object> Attributes { get; set; }
}
public interface IBlobItem
{
TypeXDictionary<IEnumerable<IDataItem>> TypeXDataDictionary { get; set; }
}
public class BlobItem : IBlobItem
{
public BlobItem()
{
TypeXDataDictionary = new TypeXDictionary<IEnumerable<IDataItem>>();
}
[JsonProperty(ItemConverterType = typeof(TypeConverter<IEnumerable<IDataItem>, List<DataItem>>))]
public TypeXDictionary<IEnumerable<IDataItem>> TypeXDataDictionary { get; set; }
}
public class TypeYDictionary<T> : Dictionary<string, T>
{
}
public class TypeXDictionary<T> : Dictionary<string, TypeYDictionary<T>>
{
}
我有几个嵌套的包含接口对象(以BlobItem
为根)的集合或字典级别,在每个级别上,我都使用 CustomCreationConverter<T>
将接口反序列化为已知的具体类型.但是,在这种情况下,当我尝试执行以下操作时:
I have several nested levels of collections or dictionaries containing interface objects (with BlobItem
as the root), and at each level I use a subclass of CustomCreationConverter<T>
to deserialize the interfaces as known concrete types. However, in this case, when I attempt to do so as follows:
var blobItem = new BlobItem();
var dataItemDic = new TypeYDictionary<IEnumerable<IDataItem>>();
var objDic = new Dictionary<string, object> {{"key", "object"}};
dataItemDic.Add("dataItemKey", new List<DataItem>() { new DataItem() { Attributes = objDic } });
blobItem.TypeXDataDictionary.Add("typeXKey", dataItemDic );
var ser = JsonConvert.SerializeObject(blobItem);
var deSerialized = JsonConvert.DeserializeObject<BlobItem>(ser);
我收到一个例外:
Run-time exception (line 19): Cannot populate JSON object onto type 'System.Collections.Generic.List`1[JsonSerialization.DataItem]'. Path 'TypeXDataDictionary.typeXKey.dataItemKey', line 1, position 50.
Stack Trace:
[Newtonsoft.Json.JsonSerializationException: Cannot populate JSON object onto type 'System.Collections.Generic.List`1[JsonSerialization.DataItem]'. Path 'TypeXDataDictionary.typeXKey.dataItemKey', line 1, position 50.]
at JsonSerialization.Program.Main(String[] args): line 19
为什么CustomCreationConverter<T>
不起作用?
推荐答案
问题出在您的BlobItem
类型上:
public class BlobItem : IBlobItem
{
public BlobItem()
{
TypeXDataDictionary = new TypeXDictionary<IEnumerable<IDataItem>>();
}
[JsonProperty(ItemConverterType = typeof(TypeConverter<IEnumerable<IDataItem>, List<DataItem>>))]
public TypeXDictionary<IEnumerable<IDataItem>> TypeXDataDictionary { get; set; }
}
对于TypeXDataDictionary
,您可以指定ItemConverterType = typeof(TypeConverter<IEnumerable<IDataItem>, List<DataItem>>)
来指示如何反序列化TypeXDataDictionary
的值.但是,这本词典实际上是词典的字典:
For TypeXDataDictionary
you specify an ItemConverterType = typeof(TypeConverter<IEnumerable<IDataItem>, List<DataItem>>)
to indicate how to deserialize the values of the TypeXDataDictionary
. However, this dictionary is actually a dictionary of dictionaries:
public class TypeXDictionary<T> : Dictionary<string, TypeYDictionary<T>>
{
}
public class TypeYDictionary<T> : Dictionary<string, T>
{
}
因此它的值不是IEnumerable<IDataItem>
类型,它们的值是Dictionary<string, IEnumerable<IDataItem>>
类型,并且转换器将无法工作.您需要的是TypeXDictionary
项的项的转换器,可以将其定义如下:
Thus its values are not of type IEnumerable<IDataItem>
, they are of type Dictionary<string, IEnumerable<IDataItem>>
and the converter will not work. What you need is a converter for the items of the items of the TypeXDictionary
, which can be defined as follows:
public class DictionaryValueTypeConverter<TDictionary, TKey, TValue, TValueSerialized> : JsonConverter
where TDictionary : class, IDictionary<TKey, TValue>, new()
where TValueSerialized : TValue
{
public override bool CanConvert(Type objectType)
{
throw new NotImplementedException();
}
public override bool CanWrite { get { return false; } }
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
throw new NotImplementedException();
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return null;
var surrogate = serializer.Deserialize<Dictionary<TKey, TValueSerialized>>(reader);
if (surrogate == null)
return null;
var dictionary = existingValue as TDictionary ?? new TDictionary();
foreach (var pair in surrogate)
dictionary[pair.Key] = pair.Value;
return dictionary;
}
}
然后将其应用于BlobItem
,如下所示:
Then applied to BlobItem
as follows:
public class BlobItem : IBlobItem
{
public BlobItem()
{
TypeXDataDictionary = new TypeXDictionary<IEnumerable<IDataItem>>();
}
[JsonProperty(ItemConverterType = typeof(DictionaryValueTypeConverter<TypeYDictionary<IEnumerable<IDataItem>>, string, IEnumerable<IDataItem>, List<DataItem>>))]
public TypeXDictionary<IEnumerable<IDataItem>> TypeXDataDictionary { get; set; }
}
样本小提琴.
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