How can I get a list of keys from Json.NET?

Question

I'm using C# and Json.NET. If I have a JObject, I want a list of the keys within the object, similar to how object.Keys() returns the keys within the object. This seems like it'd be obvious, but I'm having a rough time finding a way to do this.

Edit: I'm traversing through the object, and I want to spit out all the keys in the object as I go through. I realize that this example will result in seeing the same key multiple times, and that's OK for my needs.

public void SomeMethod(JObject parent) {
    foreach (JObject child in parent.Children()) {
        if (child.HasValues) {
        //
        // Code to get the keys here
        //
        SomeMethod(child);
        }
    }
}

Could you give a code example which you're using? Anyway try smth like this JArray sizes = (JArray)jObject["Keys"]; — sll, Jun 29 '11 at 14:30
Unfortunately that was not successful. `object["Keys"]` returns the value of the key with the name "Keys" — John, Jun 29 '11 at 20:40

James Newton-King · Accepted Answer · 2015-01-30T19:57:10.883

150

IList<string> keys = parent.Properties().Select(p => p.Name).ToList();

Documentation: JObject.Properties

edited Jan 30 '15 at 19:57

answered Jun 30 '11 at 02:35

James Newton-King

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Has this been remove as of 5.0.8 version? Because I can't no longer get the Keys for a JObject. – aminjam Nov 05 '13 at 14:12
@bigaj Nope, it has not...just tested this exact code on 5.0.8 and it appears to work fine for me – Robert Petz Nov 09 '13 at 07:21
3

@Big AJ: did you import System.Linq? It's required to do the Select() query and won't be available without it. – Wolfgang Schreurs Dec 01 '13 at 13:54
3

spent 2 hours trying to figure it out till I found this post – reza Jan 04 '14 at 09:42
Using vb.net I am not able to use this syntax `.Select(p => p.Name)` ... Visual Studio is complaining about it, automatically changes `=>` to `>=` and telling me that `p` is not defined – JohnRDOrazio Jan 04 '16 at 14:20
2

after some research I found my answer, in vb.net you would use this syntax: ```Dim keys As List(Of String) = parent.Properties().Select(Function(p) p.Name).ToList()``` – JohnRDOrazio Jan 04 '16 at 14:43
2

throws: error CS1977: Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type. – ljgww Feb 21 '18 at 14:50
Great use case for LINQ. The more I use LINQ the more I like it (when it's appropriate). – db2 Apr 03 '19 at 16:03

score 26 · Answer 2 · edited May 23 '17 at 12:18

From Converting a JSON.NET JObject's Properties/Tokens into Dictionary Keys

You can simply convert the JObject into a Dictionary object and access the method Keys() from the Dictionary object.

Like this:

using Newtonsoft.Json.Linq;
//jsonString is your JSON-formatted string
JObject jsonObj = JObject.Parse(jsonString);
Dictionary<string, string> dictObj = jsonObj.ToObject<Dictionary<string, string>>();

You can now access those keys via the dictObj.Keys() method. You can see if a key exists by performing dictObj.ContainsKey(keyName) also.

Obviously, you can format the Dictionary however you want (could be Dictionary<string, object>, etc.).

How can I get a list of keys from Json.NET?

2 Answers2

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