问题
(Skip to bolded part for one-sentence tl;dr:)
I have the JSON object below. Before looking at it, note that:
- The list of currency pairs like
BTC_AMPgoes on forever, I cut it off for the sake of example BTC_AMPappears to be a NAMED OBJECT containing some fields.{ "BTC_AMP": { "asks": [ [ "0.00007400", 5 ] ], "bids": [ [ "0.00007359", 163.59313969 ] ], "isFrozen": "0", "seq": 38044678 }, "BTC_ARDR": { "asks": [ [ "0.00003933", 7160.61031389 ] ], "bids": [ [ "0.00003912", 1091.21852308 ] ], "isFrozen": "0", "seq": 16804479 }, }
I can map the object just fine using Json.NET as described here. My problem is that it seems to me that I need to create an object and predefine property names such as BTC_AMP, BTC_ARDR, and so on for a thousand currency pairs.
You can probably see where I am going with this...how do I map this object without pre-creating every single pair name?
Hoping I am missing something obvious here.
Edit: Code looks like this, what I DON'T want to do:
public class PoloniexPriceVolume
{
public string Price { get; set; }
public double Volume { get; set; }
}
public class PoloniexPairInfo
{
public PoloniexPriceVolume Asks { get; set; }
public PoloniexPriceVolume Bids { get; set; }
public bool IsFrozen { get; set; }
public int Seq { get; set; }
}
public class PoloniexOrderBook
{
public PoloniexPairInfo BTC_AMP { get; set; }
//One thousand and one Arabian currency pairs here
}
Edit 2...can I at least dynamically create an object / an object's properties if I have a list of currency pairs somewhere? Seems less ridiculous than writing it by hand.
回答1:
You have several issues here:
Your root object has a large, variable number of properties whose values correspond to a fixed data type
PoloniexPairInfo. Since you don't want to create a root type that hardcodes all these properties, you can deserialize to aDictionary<string, PoloniexPairInfo>as shown in Create a strongly typed c# object from json object with ID as the name.The
BidandAskproperties are represented in JSON as an array of arrays of values of different types:[ [ "0.00007359", 163.59313969 ] ]You would like to map the inner arrays to a fixed POCO
PoloniexPriceVolumeby binding values at specific array indices to specific c# properties. You can do this usingObjectToArrayConverter<PoloniexPriceVolume>from C# JSON.NET - Deserialize response that uses an unusual data structure.Finally, the JSON value
"isFrozen"has a string value "0" but you would like to map it to aboolvaluepublic bool IsFrozen { get; set; }. You can do this by adaptingBoolConverterfrom Convert an int to bool with Json.Net.
Putting all this together, your can deserialize your JSON with the following models and converters:
[JsonConverter(typeof(ObjectToArrayConverter<PoloniexPriceVolume>))]
public class PoloniexPriceVolume
{
[JsonProperty(Order = 1)]
public string Price { get; set; }
[JsonProperty(Order = 2)]
public double Volume { get; set; }
}
public class PoloniexPairInfo
{
public List<PoloniexPriceVolume> Asks { get; set; }
public List<PoloniexPriceVolume> Bids { get; set; }
[JsonConverter(typeof(BoolConverter))]
public bool IsFrozen { get; set; }
public int Seq { get; set; }
}
public class ObjectToArrayConverter<T> : JsonConverter
{
//https://stackoverflow.com/a/39462464/3744182
public override bool CanConvert(Type objectType)
{
return typeof(T) == objectType;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var objectType = value.GetType();
var contract = serializer.ContractResolver.ResolveContract(objectType) as JsonObjectContract;
if (contract == null)
throw new JsonSerializationException(string.Format("invalid type {0}.", objectType.FullName));
writer.WriteStartArray();
foreach (var property in SerializableProperties(contract))
{
var propertyValue = property.ValueProvider.GetValue(value);
if (property.Converter != null && property.Converter.CanWrite)
property.Converter.WriteJson(writer, propertyValue, serializer);
else
serializer.Serialize(writer, propertyValue);
}
writer.WriteEndArray();
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var contract = serializer.ContractResolver.ResolveContract(objectType) as JsonObjectContract;
if (contract == null)
throw new JsonSerializationException(string.Format("invalid type {0}.", objectType.FullName));
if (reader.MoveToContentAndAssert().TokenType == JsonToken.Null)
return null;
if (reader.TokenType != JsonToken.StartArray)
throw new JsonSerializationException(string.Format("token {0} was not JsonToken.StartArray", reader.TokenType));
// Not implemented: JsonObjectContract.CreatorParameters, serialization callbacks,
existingValue = existingValue ?? contract.DefaultCreator();
using (var enumerator = SerializableProperties(contract).GetEnumerator())
{
while (true)
{
switch (reader.ReadToContentAndAssert().TokenType)
{
case JsonToken.EndArray:
return existingValue;
default:
if (!enumerator.MoveNext())
{
reader.Skip();
break;
}
var property = enumerator.Current;
object propertyValue;
// TODO:
// https://www.newtonsoft.com/json/help/html/Properties_T_Newtonsoft_Json_Serialization_JsonProperty.htm
// JsonProperty.ItemConverter, ItemIsReference, ItemReferenceLoopHandling, ItemTypeNameHandling, DefaultValue, DefaultValueHandling, ReferenceLoopHandling, Required, TypeNameHandling, ...
if (property.Converter != null && property.Converter.CanRead)
propertyValue = property.Converter.ReadJson(reader, property.PropertyType, property.ValueProvider.GetValue(existingValue), serializer);
else
propertyValue = serializer.Deserialize(reader, property.PropertyType);
property.ValueProvider.SetValue(existingValue, propertyValue);
break;
}
}
}
}
static IEnumerable<JsonProperty> SerializableProperties(JsonObjectContract contract)
{
return contract.Properties.Where(p => !p.Ignored && p.Readable && p.Writable);
}
}
public static partial class JsonExtensions
{
//https://stackoverflow.com/a/39462464/3744182
public static JsonReader ReadToContentAndAssert(this JsonReader reader)
{
return reader.ReadAndAssert().MoveToContentAndAssert();
}
public static JsonReader MoveToContentAndAssert(this JsonReader reader)
{
if (reader == null)
throw new ArgumentNullException();
if (reader.TokenType == JsonToken.None) // Skip past beginning of stream.
reader.ReadAndAssert();
while (reader.TokenType == JsonToken.Comment) // Skip past comments.
reader.ReadAndAssert();
return reader;
}
public static JsonReader ReadAndAssert(this JsonReader reader)
{
if (reader == null)
throw new ArgumentNullException();
if (!reader.Read())
throw new JsonReaderException("Unexpected end of JSON stream.");
return reader;
}
}
public class BoolConverter : JsonConverter
{
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
writer.WriteValue(((bool)value) ? "1" : "0");
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return null;
var token = JToken.Load(reader);
if (token.Type == JTokenType.Boolean)
return (bool)token;
return token.ToString() != "0";
}
public override bool CanConvert(Type objectType)
{
return objectType == typeof(bool);
}
}
And finally, do:
var orderBook = JsonConvert.DeserializeObject<Dictionary<string, PoloniexPairInfo>>(jsonString);
Working .Net fiddle.
回答2:
You can do something like:
dynamic data = Json.Decode(json);
Then in data you have all your object in runtime.
来源：https://stackoverflow.com/questions/45404111/parsing-json-into-c-sharp-object-get-properties-dynamically