Die obige Lösung für die JsonCreationConverter<T> ist überall im Internet zu finden, hat aber einen Fehler, der in seltenen Fällen auftaucht. Der neue JsonReader, der in der ReadJson-Methode erstellt wird, erbt keine der Konfigurationswerte des ursprünglichen Readers (Culture, DateParseHandling, DateTimeZoneHandling, FloatParseHandling, usw...). Diese Werte sollten vor der Verwendung des neuen JsonReaders in serializer.Populate() kopiert werden.
Dies ist das Beste, was mir einfiel, um einige der Probleme mit der obigen Implementierung zu beheben, aber ich denke, dass immer noch einige Dinge übersehen werden:
Update Ich habe dies aktualisiert, um eine explizitere Methode zu haben, die eine Kopie eines vorhandenen Lesers erstellt. Dies kapselt nur den Prozess des Kopierens über einzelne JsonReader-Einstellungen. Idealerweise würde diese Funktion in der Newtonsoft-Bibliothek selbst gepflegt werden, aber im Moment können Sie Folgendes verwenden:
/// <summary>Creates a new reader for the specified jObject by copying the settings
/// from an existing reader.</summary>
/// <param name="reader">The reader whose settings should be copied.</param>
/// <param name="jToken">The jToken to create a new reader for.</param>
/// <returns>The new disposable reader.</returns>
public static JsonReader CopyReaderForObject(JsonReader reader, JToken jToken)
{
JsonReader jTokenReader = jToken.CreateReader();
jTokenReader.Culture = reader.Culture;
jTokenReader.DateFormatString = reader.DateFormatString;
jTokenReader.DateParseHandling = reader.DateParseHandling;
jTokenReader.DateTimeZoneHandling = reader.DateTimeZoneHandling;
jTokenReader.FloatParseHandling = reader.FloatParseHandling;
jTokenReader.MaxDepth = reader.MaxDepth;
jTokenReader.SupportMultipleContent = reader.SupportMultipleContent;
return jTokenReader;
}
Dieser sollte wie folgt verwendet werden:
public override object ReadJson(JsonReader reader,
Type objectType,
object existingValue,
JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return null;
// Load JObject from stream
JObject jObject = JObject.Load(reader);
// Create target object based on JObject
T target = Create(objectType, jObject);
// Populate the object properties
using (JsonReader jObjectReader = CopyReaderForObject(reader, jObject))
{
serializer.Populate(jObjectReader, target);
}
return target;
}
Es folgt eine ältere Lösung:
/// <summary>Base Generic JSON Converter that can help quickly define converters for specific types by automatically
/// generating the CanConvert, ReadJson, and WriteJson methods, requiring the implementer only to define a strongly typed Create method.</summary>
public abstract class JsonCreationConverter<T> : JsonConverter
{
/// <summary>Create an instance of objectType, based properties in the JSON object</summary>
/// <param name="objectType">type of object expected</param>
/// <param name="jObject">contents of JSON object that will be deserialized</param>
protected abstract T Create(Type objectType, JObject jObject);
/// <summary>Determines if this converted is designed to deserialization to objects of the specified type.</summary>
/// <param name="objectType">The target type for deserialization.</param>
/// <returns>True if the type is supported.</returns>
public override bool CanConvert(Type objectType)
{
// FrameWork 4.5
// return typeof(T).GetTypeInfo().IsAssignableFrom(objectType.GetTypeInfo());
// Otherwise
return typeof(T).IsAssignableFrom(objectType);
}
/// <summary>Parses the json to the specified type.</summary>
/// <param name="reader">Newtonsoft.Json.JsonReader</param>
/// <param name="objectType">Target type.</param>
/// <param name="existingValue">Ignored</param>
/// <param name="serializer">Newtonsoft.Json.JsonSerializer to use.</param>
/// <returns>Deserialized Object</returns>
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return null;
// Load JObject from stream
JObject jObject = JObject.Load(reader);
// Create target object based on JObject
T target = Create(objectType, jObject);
//Create a new reader for this jObject, and set all properties to match the original reader.
JsonReader jObjectReader = jObject.CreateReader();
jObjectReader.Culture = reader.Culture;
jObjectReader.DateParseHandling = reader.DateParseHandling;
jObjectReader.DateTimeZoneHandling = reader.DateTimeZoneHandling;
jObjectReader.FloatParseHandling = reader.FloatParseHandling;
// Populate the object properties
serializer.Populate(jObjectReader, target);
return target;
}
/// <summary>Serializes to the specified type</summary>
/// <param name="writer">Newtonsoft.Json.JsonWriter</param>
/// <param name="value">Object to serialize.</param>
/// <param name="serializer">Newtonsoft.Json.JsonSerializer to use.</param>
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
serializer.Serialize(writer, value);
}
}
