using System;

​

public class Program

{

    public static void Main()

    {

        var input = new Foo { Bar = "\u00A0 Test !@#$%^&*() 💯\uD83D\uDCAF 你好" };

        var newtonsoft = Newtonsoft.Json.JsonConvert.SerializeObject(input);

        var system = System.Text.Json.JsonSerializer.Serialize(input, new System.Text.Json.JsonSerializerOptions

                                                               {

                                                                   Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping, 

                                                               });

        var utf8Json = Utf8Json.JsonSerializer.ToJsonString(input);

​

        Console.WriteLine($"Original: {input.Bar} - {input.Bar.Contains('\u00A0')}");

        Console.WriteLine($"Newtonsoft: {newtonsoft} - {newtonsoft.Contains('\u00A0')}");

        Console.WriteLine($"System.Text.Json: {system} - {system.Contains('\u00A0')}");

        Console.WriteLine($"Utf8Json: {utf8Json} - {utf8Json.Contains('\u00A0')}");

    }

}

​

public class Foo

{

    public string Bar { get; set; }

}

​