不能使用 AutoMapper 映射到空值

Question

public class TestNullableString {
    public string? Test;

    public TestNullableString(string? test) {
        Test = test;
    }
}

public class TestNonNullableString {
    public string Test;
}

public class TestProfile : Profile
{
    public TestProfile() {
        CreateMap<TestNonNullableString, TestNullableString>
             .ForMember(dest => dest.Test, opt => {
                 opt.AllowNull();
                 opt.MapFrom(src => src.Test == "" ? null : src.Test);
              });
    }
}

If I try to map from NonNullableString to NullableString, it still gives me the empty string at mapping. It wont give me a null-value, even if NonNullableString is "". What am I doing wrong?

I'm using AutoMapper 9.0.0.

PS. I've also tried setting AllowNullDestinationValues to true without any success.

Answer 1

CreateMap<TestNonNullableString, TestNullableString>()
            .ForMember(dest => dest.Test,
                opt => { opt.MapFrom(src => string.IsNullOrWhiteSpace(src.Test) ? null : src.Test); })
            .ConstructUsing(x => new TestNullableString(string.IsNullOrWhiteSpace(x.Test) ? null: x.Test ));