Tracker1 Tracker1 - 10 days ago 5
C# Question

How to cast JObject in JSON.Net to T

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);

Answer

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>();
    ...
}
Comments