Transform the same instance

[YeskaNova]

I need to transform my entities before returning them to the caller. I need to replace sensitive fields/properties with Null and remove some keys from dictionaries. I have done a simple test and but I can't make it work, am I missing something? I want to replace the property Secret with null, and remove the Key "Secret" from the dictionary :

using Mapster;
using MapsterMapper;
using System.Collections.Generic;
using System.Diagnostics;

namespace ConsoleApp22
{
    public class Post
    {
        public IDictionary<string,string> Dic { get; set; }
        public string Secret { get; set; }
    }
    class Program
    {

        static void Main(string[] args)
        {
            var config = TypeAdapterConfig<Post, Post>
                .NewConfig()
                .Map(nameof(Post.Secret), x => default(string))
                .Map(nameof(Post.Dic) + ".Secret", x => default(string));
            config.Compile();
            var mapper = new Mapper(config.Config);

            var p1 = new Post() {Secret = "Test", Dic = new Dictionary<string, string>() { { "Secret", "test" }, {"B", "test2" } } };

            mapper.From(p1).AdaptTo(p1);
            Debug.Assert(p1.Dic["Secret"] == null);
            Debug.Assert(p1.Secret == null);

        }
    }
}