How to get all the values from a JSON array

Question

I'm trying to get all the keys from a JSON array. The link of the JSON is: this one

And the code I'm using is:

Imports System.Net.Http
Imports System.Text.Json.Nodes
Public Class Form1
    Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Using http = New HttpClient
            Dim url = "https://api-cloud.bitmart.com/account/v1/currencies"
            Dim json = JsonNode.Parse(Await http.GetStreamAsync(url))
            Dim naming As [String] = json("currency") 

            RichTextBox1.Text = json("currency")
        End Using
    End Sub
End Class

But clicking the Button doesn't populate anything. The RichTextBox stays empty, while I want to get all the values ( es : "DFC, "$GM", "BBK" ecc)

I'm using .net6 but a framework.net solution would be appreciated. Thanks