using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var a = new Dictionary<int, string> {

            [1] = "Hello",

            [2] = "World",

            [3] = "",

        };

        var b = a.Where(kvp => kvp.Value != "");

        a[3] = "Was empty";

        a[2] = "There";

        a[4] = "New";

        a[5] = "";

        var c = b.Select(kvp => $"{kvp.Value} -- {kvp.Key}").ToList();

        Console.WriteLine(ToJson(c));

    }

​

    internal static string ToJson(object value) => System.Text.Json.JsonSerializer.Serialize(value);

}