How can I efficiently search for a specific JToken by name within a nested JObject hierarchy in C# using Newtonsoft.Json?

Searching for a Specific JToken by Name in a JObject Hierarchy

When working with JSON data in C#, the Newtonsoft.Json library provides various methods to interact with JObjects and JTokens. If you need to retrieve a specific JToken by name from a JObject hierarchy, you may be wondering if there is a built-in function that can simplify this task.

Using SelectToken() for Specific Token Navigation

If you know the exact path to the JToken you want to retrieve, the SelectToken() method provides a direct way to navigate to it. For instance:

JObject jObject = ...;
string distanceText = jObject.SelectToken("routes[0].legs[0].distance.text").ToString();

In this example, we retrieve the "text" JToken from the distance property nested within the first leg of the first route.

Implementing a Recursive Search for All Tokens

If you need to find all occurrences of a JToken with a given name regardless of its location within the JObject hierarchy, you will need to implement a recursive search method. Here's one approach:

public static class JsonExtensions
{
    public static List<JToken> FindTokens(this JToken containerToken, string name)
    {
        List<JToken> matches = new List<JToken>();
        FindTokens(containerToken, name, matches);
        return matches;
    }

    private static void FindTokens(JToken containerToken, string name, List<JToken> matches)
    {
        if (containerToken.Type == JTokenType.Object)
        {
            foreach (JProperty child in containerToken.Children<JProperty>())
            {
                if (child.Name == name)
                {
                    matches.Add(child.Value);
                }
                FindTokens(child.Value, name, matches);
            }
        }
        else if (containerToken.Type == JTokenType.Array)
        {
            foreach (JToken child in containerToken.Children())
            {
                FindTokens(child, name, matches);
            }
        }
    }
}

This method can be used as follows:

foreach (JToken token in jObject.FindTokens("text"))
{
    Console.WriteLine(token.Path + ": " + token.ToString());
}

The resulting output will display the path and value of all JTokens with the name "text". For example:

routes[0].legs[0].distance.text: 1.7 km
routes[0].legs[0].duration.text: 4 mins
routes[0].legs[1].distance.text: 2.3 km
routes[0].legs[1].duration.text: 5 mins

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