Exclude null JValues from JSON response C#

Question

Having this JSON structure :

[
  {
    "Id": 885758,
    "IssueId": 611932,
    "Pinpoint": {
      "Name": null,
      "Position": {
        "X": -32.452857971191406,
        "Y": -14.971426010131836,
        "Z": 9.111014366149902
      },
      "Element1": null,
      "Element2": null
    }
  },
  {
    "Id": 885764,
    "IssueId": 611932,
    "Pinpoint": {
      "Name": null,
      "Position": {
        "X": -21.042057037353516,
        "Y": -21.742080688476562,
        "Z": 7.72857141494751
      },
      "Element1": null,
      "Element2": null
    },
  },
  {
    "Id": 885765,
    "IssueId": 611932,
    "Pinpoint": null
  }
]

I want to be able to obtain a List of JToken containing all Pinpoints that are not null So basically something like this :

  {
    "Pinpoint": {
      "Name": null,
      "Position": {
        "X": -32.452857971191406,
        "Y": -14.971426010131836,
        "Z": 9.111014366149902
      },
      "Element1": null,
      "Element2": null
    }
  },
  {
    "Pinpoint": {
      "Name": null,
      "Position": {
        "X": -21.042057037353516,
        "Y": -21.742080688476562,
        "Z": 7.72857141494751
      },
      "Element1": null,
      "Element2": null
    }
  }

Image here of what a normal LINQ select without the where condition returns :

This is what I tried so far with related errors / exceptions :

//Cannot access child value on Newtonsoft.Json.Linq.JValue
List<JToken> results = JArray.Parse(response.Content)
    .Select(x => x["Pinpoint"])
    .Where(x => x["Pinpoint"] != null)
    .ToList();

//Object reference not set to an instance of an object.
List<JToken> results = JArray.Parse(response.Content)
    .Select(x => x["Pinpoint"])
    .Where(x => x["Pinpoint"].HasValues)
    .ToList();

//Object reference not set to an instance of an object.
List<JToken> results = JArray.Parse(response.Content)
    .Select(x => x["Pinpoint"])
    .Where(x => x["Pinpoint"].Type != JTokenType.Null)
    .ToList();

Does Checking for empty or null JToken in a JObject answer your question? — dbc
– dbc, Commented Jun 16, 2022 at 15:45
Errors are shown in the last C# code block see the comments. And no unfortunately it doesn't answer my question I can't make it work. — uwponcel
– uwponcel, Commented Jun 16, 2022 at 15:47
You need to put your Where clauses before your Select clause. Once you've done .Select(x => x["Pinpoint"]) your current item will be the value of x["Pinpoint"] so you can't do x => x["Pinpoint"] != null subsequently. Or keep the Where clause first and do .Where(p => !p.IsNullOrEmpty()) next, where IsNullOrEmpty() is from the linked question Checking for empty or null JToken in a JObject. — dbc
– dbc, Commented Jun 16, 2022 at 15:52
Demo of using Brian Roger's JsonExtensions.IsNullOrEmpty(this JToken token) here: dotnetfiddle.net/INCWaq. Do you need a separate answer or is a duplicate OK? — dbc
– dbc, Commented Jun 16, 2022 at 16:01
A null JToken will be returned when the value isn't present at all in the JSON. A non-null JToken will be returned with type JTokenType.Null when the value was found in the JSON but the value itself was null. I.e. if you do x["Pinpoint"] then if your JSON object looks like {} you will get back null but if your JSON object looks like {"Pinpoint":null} you will get back a JValue with JTokenType.Null. So you must check for both. For details see Strange behavior in json.net: why is a null JToken replaced with a non-null value?. — dbc
– dbc, Commented Jun 16, 2022 at 16:12

dbc · Accepted Answer · 2022-06-16 19:23:02Z

1

try this

List<JObject> pinPoints = JArray.Parse(json).Where(p => (p["Pinpoint"] as JObject) != null)
.Select(p => (JObject)p["Pinpoint"]).ToList();

UPDATE

thanks to @dbc, there is a shorthand

JArray.Parse(json).Select(p => p["Pinpoint"]).OfType<JObject>().ToList();

edited Jun 16, 2022 at 19:23

dbc

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answered Jun 16, 2022 at 16:36

Serge

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3 Comments

dbc Over a year ago

JArray.Parse(json).Select(p => p["Pinpoint"]).OfType<JObject>().ToList() would work also and avoid doing p["Pinpoint"] twice.

Serge Over a year ago

@dbc Thank you! It is really interesting syntax. I will certainly use it in the future.

dbc Over a year ago

I removed the cast from inside the Select(p => p["Pinpoint"]) because, if p["Pinpoint"] is a JValue with JTokenType.Null, it will throw an exception. OfType() will filter them (as well as the actual null values) out later.

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