How to cast JObject in JSON.Net to T

问题

I know that I can use JsonConvert.DeserializeObject<T>(string), however, I need to peek into the object's _type (which may not be the first parameter) in order to determine the specific class to cast to. Essentially, what I am wanting to do is something like:

//Generic JSON processor for an API Client.
function MyBaseType ProcessJson(string jsonText)
{
  var obj = JObject.Parse(jsonText);
  switch (obj.Property("_type").Value.ToString()) {
    case "sometype":
      return obj.RootValue<MyConcreteType>();
      //NOTE: this doesn't work... 
      // return obj.Root.Value<MyConcreteType>();
    ...
  }
}
...

// my usage...
var obj = ProcessJson(jsonText);
var instance = obj as MyConcreteType;
if (instance == null) throw new MyBaseError(obj);

回答1:

First parse the JSON into a JObject. Then lookup the _type attribute using LINQ to JSON. Then switch depending on the value and cast using ToObject<T>:

var o = JObject.Parse(text);
var jsonType = (String)o["_type"];

switch(jsonType) {
    case "something": return o.ToObject<Type>();
    ...
}

回答2:

JSON.NET has no direct ability to support both requisites:

custom name of the property holding the type name
look for the property anywhere in the object

The first requisites is fulfilled by JsonSubTypes The second one by specifying thh right MetadataPropertyHandling

来源：https://stackoverflow.com/questions/10218827/how-to-cast-jobject-in-json-net-to-t

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json.net