Iterating through a nested JSON Array in C# with Newtonsoft

问题

I have a block of JSON as follows:

[
  {
    "id": 1,
    "name": "Section1",
    "project_id": 100,
    "configs": [
      {
        "id": 1000,
        "name": "myItem1",
        "group_id": 1
      }
    ]
  },
  {
    "id": 2,
    "name": "Section2",
    "project_id": 100,
    "configs": [
      {
        "id": 1001,
        "name": "myItem2",
        "group_id": 2
      },
      {
        "id": 1002,
        "name": "myItem3",
        "group_id": 2
      },
      {
        "id": 1003,
        "name": "myItem4",
        "group_id": 2
      }
    ]
  },
  {
    "id": 3,
    "name": "Section3",
    "project_id": 100,
    "configs": [
      {
        "id": 1004,
        "name": "myItem5",
        "group_id": 5
      },
    ]
  }
]

I have pulled it into Memory as a JArray.

I need to iterate through this such that I'm grabbing a list of ids and name from only the config sub-arrays. Ideally, I'll end up with something like this:

1000, myItem1
1001, myItem2
1002, myItem3
1003, myItem4
1004, myItem5

I'm having a hard time understanding what Newstonsoft calls a JObject vs a JArray, or how to access the various parts of each of those data structures. What I have right now is as follows:

foreach (JObject config in result["configs"])
{
    string id = (string)config["id"];
    string name = (string)config["name"];
    string gid = (string)config["group_id"];

    Console.WriteLine(name + " - " + id + " - " + gid);
}

This does not work, but I hope it illustrates what my end goal is. I've been unable to piece together how to accomplish this goal.

回答1:

A JObject is an object (analogous to a class):

{
    "a": 1,
    "b": true
}

A JArray is a JSON array, and contains multiple JObject entities:

[
    {
        "a": 1,
        "b": true
    },
    {
        "a": 2,
        "b": true
    }
]

The root of a JSON document can be an object, or an array. In your case, it's an array.

The following code and fiddle reveals that your code is fine, provided that you deserialize the document as what it is - an array.

string json = "[{\"id\":1,\"name\":\"Section1\",\"project_id\":100,\"configs\":[{\"id\":1000,\"name\":\"myItem1\",\"group_id\":1}]},{\"id\":2,\"name\":\"Section2\",\"project_id\":100,\"configs\":[{\"id\":1001,\"name\":\"myItem2\",\"group_id\":2},{\"id\":1002,\"name\":\"myItem3\",\"group_id\":2},{\"id\":1003,\"name\":\"myItem4\",\"group_id\":2}]},{\"id\":3,\"name\":\"Section3\",\"project_id\":100,\"configs\":[{\"id\":1004,\"name\":\"myItem5\",\"group_id\":5},]}]";
JArray obj = Newtonsoft.Json.JsonConvert.DeserializeObject<JArray>(json);
foreach (var result in obj)
{
    foreach (JObject config in result["configs"])
    {
        string id = (string)config["id"];
        string name = (string)config["name"];
        string gid = (string)config["group_id"];

        Console.WriteLine(name + " - " + id + " - " + gid);
    }
}

来源：https://stackoverflow.com/questions/47425419/iterating-through-a-nested-json-array-in-c-sharp-with-newtonsoft

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