JSON.NET how to remove nodes

Question

I have a json like the following:

{
  "d": {
    "results": [
      {
        "__metadata": {
        },
        "prop1": "value1",
        "prop2": "value2",
        "__some": "value"
      },
      {
        "__metadata": {
        },
        "prop3": "value1",
        "prop4": "value2",
        "__some": "value"
      },
    ]
  }
}

I just want to transform this JSON into a different JSON. I want to strip out the "_metadata" and "_some" nodes from the JSON. I'm using JSON.NET.

I have no experience with C# but I assume you can simply parse the JSON, delete they keys from the resulting data structure and convert it back to JSON again. — Felix Kling, Jul 26 '12 at 18:58
I can do that, but I was looking for JSON.NET way of doing it. — Mohamed Nuur, Jul 26 '12 at 19:40

score 48 · Accepted Answer · answered Jul 26 '12 at 21:46

48

I just ended up deserializing to JObject and recursively looping through that to remove unwanted fields. Here's the function for those interested.

private void removeFields(JToken token, string[] fields)
{
    JContainer container = token as JContainer;
    if (container == null) return;

    List<JToken> removeList = new List<JToken>();
    foreach (JToken el in container.Children())
    {
        JProperty p = el as JProperty;
        if (p != null && fields.Contains(p.Name))
        {
            removeList.Add(el);
        }
        removeFields(el, fields);
    }

    foreach (JToken el in removeList)
    {
        el.Remove();
    }
}

answered Jul 26 '12 at 21:46

Mohamed Nuur

5,536
6
39
55

Thanks! I needed that. Now I can do a Foreach on my JArray's Children collection to remove all my the properties I want. – duyn9uyen Nov 15 '13 at 14:38
This really helped me - I wanted to log JSON data with sensitive fields replaced by the length of the data. I was able to get and set p.Value. – 79IT Jul 12 '14 at 10:32

score 25 · Answer 2 · answered Jul 23 '15 at 08:25

Building off of @[Mohamed Nuur]'s answer, I changed it to an extension method which I think works better:

 public static JToken RemoveFields(this JToken token, string[] fields)
    {
        JContainer container = token as JContainer;
        if (container == null) return token;

        List<JToken> removeList = new List<JToken>();
        foreach (JToken el in container.Children())
        {
            JProperty p = el as JProperty;
            if (p != null && fields.Contains(p.Name))
            {
                removeList.Add(el);
            }
            el.RemoveFields(fields);
        }

        foreach (JToken el in removeList)
        {
            el.Remove();
        }

        return token;
    }

Here is unit test:

[TestMethod]
     public void can_remove_json_field_removeFields()
     {
        string original = "{\"d\":{\"results\":[{\"__metadata\":{},\"remove\":\"done\",\"prop1\":\"value1\",\"prop2\":\"value2\",\"__some\":\"value\"},{\"__metadata\":{},\"prop3\":\"value1\",\"prop4\":\"value2\",\"__some\":\"value\"}],\"__metadata\":{\"prop3\":\"value1\",\"prop4\":\"value2\"}}}";
        string expected = "{\"d\":{\"results\":[{\"prop1\":\"value1\",\"prop2\":\"value2\",\"__some\":\"value\"},{\"prop3\":\"value1\",\"prop4\":\"value2\",\"__some\":\"value\"}]}}";
        string actual = JToken.Parse(original).RemoveFields(new string[]{"__metadata", "remove"}).ToString(Newtonsoft.Json.Formatting.None);
        Assert.AreEqual(expected, actual);
     }

great solution, tested and used – iojancode Dec 25 '19 at 21:08 — iojancode, Dec 25 '19 at 21:08

score 2 · Answer 3 · answered Jul 26 '12 at 20:56

2

I would create a new data structure with only the required information and copy the data from the first one. Often that is the simpliest approach. Just an idea.

answered Jul 26 '12 at 20:56

Anders Lindén

6,839
11
56
109

1

But I don't know what the data will be. I want to write a generic function that will take a JSON string and a list of properties to exclude (maybe xpath type?) and returns a new JSON string without the properties that are excluded. – Mohamed Nuur Jul 26 '12 at 21:32

score -1 · Answer 4 · answered Apr 18 '20 at 13:49

This answer applies if you have a JArray with JTokens, not JObjects:

Here is an example:

string json = "[null, null, \"x\", null, null, null, 0,[],[[\"x\"], null,[0],[\"x\"]]]";

    JArray array = JArray.Parse(json);

    // Keep first 3 elements, remove the rest
    int max = array.Count;
    for (int i = 0; i < max - 3; i++)
    {
        JToken elem = array[3];
        array.Remove(elem);
    }

    json = array.ToString(Newtonsoft.Json.Formatting.None);

    Console.WriteLine(json);

JSON.NET how to remove nodes

4 Answers4

Linked