从具有特定其他属性值的 JObject 中提取 JObject 属性

Question

I'm relatively fluent using json.net, but I'm struggling to pull this value in a straightforward way.

I feel like json.net should be able to infer what I'm trying to do so that I don't have to cast every step along the way to get what I want.

Below is my first failed attempt and a second attempt which I got to work. While the second attempt does work, I'd like to simplify the code to be somewhat more like the first one.

Note that I can't assume that the "C" object is the one that contains the object I want.

var jt = JToken.Parse(@"{
    ""A"": {
        ""name"": ""object1"",
        ""order"": ""1"",
        ""type"": ""val""
    },
    ""B"": {
        ""order"": ""2"",
        ""type"": ""val"",

    },
    ""C"": {
        ""name"": ""object3"",
        ""type"": ""val"",
        ""answer"": ""Yes"", ""<------ comment"": ""this is the value I'm trying to get""
    }
}");

//var firstAttempt = (jt.First(j => j["name"] == "object3"))["answer"];  // cannot be applied to operands of type 'JToken' and 'String'

var thisWorksFine = jt.First(a => a.ToObject<JProperty>()
                            .Value.ToObject<JObject>()["name"]?.ToString() == "object3")
                            .ToObject<JProperty>()
                            .Value["answer"];

So my question is, is there a way to get the value without having to cast each object/property and ultimately have code that looks more like my first attempt? If my second attempt is more or less what has to be done, that's fine.

Answer 1

I've used QuickType to make a model of your Json code and then parsed it and did the filtering on the resulting objects which is much easier. Code:

public class MyElement
{
    [JsonProperty("name")]
    public string Name { get; set; }

    [JsonProperty("order")]
    public long Order { get; set; }

    [JsonProperty("type")]
    public string Type { get; set; }

    [JsonProperty("answer")]
    public string Answer { get; set; }
}

And parsing:

string json = @"{
    ""A"": {
        ""name"": ""object1"",
        ""order"": ""1"",
        ""type"": ""val""
    },
    ""B"": {
        ""order"": ""2"",
        ""type"": ""val"",

    },
    ""C"": {
        ""name"": ""object3"",
        ""type"": ""val"",
        ""answer"": ""Yes"",
    }
}";

Dictionary<string, MyElement> elements = JsonConvert.DeserializeObject<Dictionary<string, MyElement>>(json);
string answerOfObject3 = elements.Values.FirstOrDefault(element => element.Name == "object3")?.Answer;

Answer 2

Do you specifically want to always get the answer under the "C" object?

If so you can use:

var jToken = JToken.Parse("{\r\n\t\"A\": {\r\n\t\t\"name\": \"object1\",\r\n\t\t\"order\": \"1\",\r\n\t\t\"type\": \"val\"\r\n\t},\r\n\t\"B\": {\r\n\t\t\"name\": \"object2\",\r\n\t\t\"order\": \"2\",\r\n\t\t\"type\": \"val\"\r\n\t},\r\n\t\"C\": {\r\n\t\t\"name\": \"object3\",\r\n\t\t\"type\": \"val\",\r\n\t\t\"answer\": \"Yes\"\r\n\t}\r\n}");

var answer = jToken.SelectToken("C.answer");

Answer 3

You seem to be jumping through more hoops than you need to. I would rewrite your query like this:

var answer = jt.Children<JProperty>()
               .Where(jp => (string)jp.Value["name"] == "object3")
               .Select(jp => (string)jp.Value["answer"])
               .FirstOrDefault();

Fiddle: https://dotnetfiddle.net/blKne6

The above can be simplified somewhat to the following, which is a little closer to your first attempt:

var answer = (string)jt.Children<JProperty>()
                       .FirstOrDefault(jp => (string)jp.Value["name"] == "object3")
                       ?.Value["answer"];

Fiddle: https://dotnetfiddle.net/3Iw8Uu