// https://stackoverflow.com/questions/60089463/query-or-deserialize-json-with-dynamic-keys-using-system-text-json

using System;

using System.Collections.Generic;

using System.Text.Json;

​

public class Program

{

    public static void Main()

    {

        var json = @"{

                   ""key1"": ""Hello"",

                   ""key2"": {

                      ""items"": {

                         ""123"": {

                            ""pageid"": 123,

                            ""name"": ""data""

                         },

                         ""234"": {

                            ""pageid"": 234,

                            ""name"": ""Something""

                         }

                      }

                    }

                 }";        

        var data = JsonSerializer.Deserialize<Root>(json);

        Console.WriteLine("pageid: " + data.key2.items["123"].pageid);

        Console.WriteLine("name: " + data.key2.items["123"].name);

        Console.WriteLine("pageid: " + data.key2.items["234"].pageid);

        Console.WriteLine("name: " + data.key2.items["234"].name);

        foreach (var key in data.key2.items.Keys) {

            Console.WriteLine($"{key} {data.key2.items[key].name}"); // {items["key"].name}");

        }

    }   

}

​

public class ItemProps

{

    public int pageid { get; set; }

    public string name { get; set; }

}

​

public class Item

{

    public Dictionary<string, ItemProps> items { get; set; }

}

​

public class Root

{

    public string key1 { get; set; }

    public Item key2 { get; set; }

}