How migrate AutoMapper to Mapster - ConvertUsing

Please help me migrate from AutoMapper to Mapster

using Mapster;

namespace Mappers
{
public class SampleRegister : IRegister
{
public void Register(TypeAdapterConfig config)
{
// Map ICollection to string
config.NewConfig<ICollection, string>()
.ConvertUsing(src =>
{
if (src == null || !src.Any())
{
return null;
}

                // Note: You could also replace this with string.Join(",", src)
                return src.Aggregate((x, y) => $"{x},{y}");
            });

        // Map string to ICollection<string> (Specifically HashSet<string>)
        config.NewConfig<string, HashSet<string>>()
            .ConvertUsing(src =>
            {
                var list = new HashSet<string>();
                if (!string.IsNullOrWhiteSpace(src))
                {
                    src = src.Trim();
                    foreach (var item in src.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries).Distinct())
                    {
                        list.Add(item);
                    }
                }
                return list;
            });
    }
}

}

Start by reviewing the provided SampleRegister code and Mapster's ConvertUsing API to determine how the AutoMapper conversion is expected to translate. The issue names no repository file, test, failure, or concrete change; it is complete only when the required ICollection and string conversion behavior is clarified.