How to retrieve a specific property from a nested JSON object

Question

I have a nested json object which looks like this

{{
  "id": "99ed8a1a-68fa-4464-b5cb-f116ede0a520",
  "title": "NUnitTestDemo",
  "has_children": true,
  "level": 0,
  "children": [
    {
      "id": "c41764b1-a59a-420b-b06e-9f97f3876e9b",
      "title": "TestScripts",
      "has_children": true,
      "level": 1,
      "children": [
        {
          "id": "cfba3d9e-d305-464d-9154-cdd2efcb5436",
          "title": "SmokeTest",
          "has_children": true,
          "level": 2,
          "children": [
            {
              "id": "b58596fc-aeab-4f20-8a91-85599c08c0fc",
              "title": "TestAdd",
              "has_children": false,
              "level": 3,
              "tag": "mytag,add",
              "property": "Testing Addition of Two numbers",
              "children": []
            },
            {
              "id": "c819746e-25b9-4c84-8fb4-28794c3b2fe4",
              "title": "TestSubtract",
              "has_children": false,
              "level": 3,
              "tag": "mytag,subtract",
              "property": "Testing Subtraction of Two numbers",
              "children": []
            }
          ]
        },
        {
          "id": "7dce76a3-f318-4d49-920c-1d94b3ec9519",
          "title": "SmokeTest1",
          "has_children": true,
          "level": 2,
          "children": [
            {
              "id": "64bf771d-313b-44ce-b910-27945505dada",
              "title": "TestMultiply",
              "has_children": false,
              "level": 3,
              "tag": "mytag,add",
              "property": "Testing Addition of Two numbers",
              "children": []
            },
            {
              "id": "5d810bc0-a9af-4838-b8eb-5fc7c47e910a",
              "title": "TestDivide",
              "has_children": false,
              "level": 3,
              "tag": "mytag,subtract",
              "property": "Testing Subtraction of Two numbers",
              "children": []
            }
          ]
        },
        {
          "id": "8af09935-93fa-4379-9aa4-9f809055d1ea",
          "title": "Sample",
          "has_children": true,
          "level": 2,
          "children": [
            {
              "id": "407944bd-437e-48cd-8af0-bbd2eb376e72",
              "title": "Tests",
              "has_children": true,
              "level": 3,
              "children": [
                {
                  "id": "01223a10-2dda-4e3c-9287-d49b0c08870d",
                  "title": "SmokeTest2",
                  "has_children": true,
                  "level": 4,
                  "children": [
                    {
                      "id": "6e3df5f1-bcca-40a8-9ed5-3eaa74558488",
                      "title": "TestA",
                      "has_children": false,
                      "level": 5,
                      "tag": "mytag,add",
                      "property": "Testing Addition of Two numbers",
                      "children": []
                    },
                    {
                      "id": "0414d2c3-e4c8-4e52-9584-6a9e8516a3e2",
                      "title": "TestB",
                      "has_children": false,
                      "level": 5,
                      "tag": "mytag,subtract",
                      "property": "Testing Subtraction of Two numbers",
                      "children": []
                    }
                  ]
                }
              ]
            }
          ]
        },
        {
          "id": "7dbfcdfe-f6cb-4942-bcc6-3ec899aec674",
          "title": "MyTestFolder",
          "has_children": true,
          "level": 2,
          "children": [
            {
              "id": "16c3a197-824a-4309-bb97-24d454d448f5",
              "title": "MyTestClass",
              "has_children": true,
              "level": 3,
              "children": [
                {
                  "id": "c37f2d67-0db0-49bf-80e0-9e99d7e9d767",
                  "title": "TestC",
                  "has_children": false,
                  "level": 4,
                  "tag": "mytag,add",
                  "property": "Testing Addition of Two numbers",
                  "children": []
                },
                {
                  "id": "a91c8c04-8a60-4872-b990-db9f993ddbe5",
                  "title": "TestD",
                  "has_children": false,
                  "level": 4,
                  "tag": "mytag,subtract",
                  "property": "Testing Subtraction of Two numbers",
                  "children": []
                }
              ]
            }
          ]
        }
      ]
    }
  ]
}}

If you notice at every level there is a "children" array. Now, when I am searching for "MyTestFolder" inside the above mentioned json, it is returning me "null".

My function looks like this. It is written in C# and I am using Newtonsoft.json library.

I am using .NET Core 3.1

public JObject RetrieveSpecifiedJsonObject(string propertyName, JObject jsonObject)
{
    //propertyName is the property to be retrieved
    string title = jsonObject.SelectToken("title").ToString();
    if(title != propertyName)
    {
        JArray childArray = jsonObject.SelectToken("children") as JArray;
        for(int i=0; i<childArray.Count; i++)
        {
            JObject childArrElem = childArray[i] as JObject;
            string arrElemTitle = childArrElem.SelectToken("title").ToString();
            if(arrElemTitle != propertyName)
            {
                RetrieveSpecifiedJsonObject(propertyName, childArrElem);
            }
            else
            {
                return childArrElem;
            }
        }//FOR ENDS
        return null;
    }//IF title != propertyName ENDS
    else
    {
        return jsonObject;
    }
}

I guess it has to be a recursive function. But, not getting what to do. When I am searching.

FYI, I can't search like jsonobject["children"][0]["MyTestFolder"]. I may have to search for any node at any point of time. For that, I need to write a generic function.

So, please try to provide me a generic solution for this. Sorry, but this isn't a free code writing service — Pavel Anikhouski
– Pavel Anikhouski, Commented May 25, 2020 at 6:37
Hi Ayan, It is really hard to copy paste your code to our visual studio. It would be great if you create minimal reproducible example — Prasad Telkikar
– Prasad Telkikar, Commented May 25, 2020 at 6:45
@PrasadTelkikar If you see my code, it is just a small function. Are you talking about the json structure by any chance ? That is just for your reference. — Ayan
– Ayan, Commented May 25, 2020 at 6:48
Did you try to debug your code? e.g: Does title actually match "NUnitTestDemo" in the first iteration? What does childArray look like? Is childArray.Count actually equal to 1? — Rafalon
– Rafalon, Commented May 25, 2020 at 6:51
@Rafalon Yes, it matches the title. The problem is, I am not able to stop the recursion. So, even after the value is found, the recursion keeps going and it returns null. — Ayan
– Ayan, Commented May 25, 2020 at 6:53

JimmyN · Accepted Answer · 2020-05-25 06:53:35Z

3

it returns null because this block doesn't do any action with the result from RetrieveSpecifiedJsonObject

if(arrElemTitle != propertyName)
{
   RetrieveSpecifiedJsonObject(propertyName, childArrElem);
}

maybe you should do that:

if(arrElemTitle != propertyName)
{
   var result = RetrieveSpecifiedJsonObject(propertyName, childArrElem);
   if (result != null)
       return result;
}

answered May 25, 2020 at 6:53

JimmyN

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1 Comment

Ayan Over a year ago

Works fine ! Thanks :-)

Rafalon · Accepted Answer · 2020-05-25 07:02:25Z

In addition to what JimmyN wrote in his answer, I'd say that you could simplify your recursive function as such (you already check the title property at the top of the function, so you don't need to check it again inside the for loop):

public JObject RetrieveSpecifiedJsonObject(string propertyName, JObject jsonObject)
{
  //propertyName is the property to be retrieved
  string title = jsonObject.SelectToken("title").ToString();
  if(title != propertyName)
  {            
    JArray childArray = jsonObject.SelectToken("children") as JArray;
    for(int i=0; i<childArray.Count; i++)
    {
      JObject childArrElem = childArray[i] as JObject;
      // the following will already check childArray and all of its children
      JObject result = RetrieveSpecifiedJsonObject(propertyName, childArrElem);
      if(result != null)
        return result;
    }//FOR ENDS
    return null;
  }//IF title != propertyName ENDS
  else
  {
     return jsonObject;
  }
}

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