Google.Protobuf.ByteString needs to have a constructor with 0 args or only optional args. When mapping to byte[]

[schhwork]

Im getting the exception in the title still. I found an old issue #1457 where the same exception was discussed and @jbogard confimed it was a bug or missing feature if i understood that correctly. Ive reproduced this in a spikeproject just to confirm nothing else was affecting it. It seems that the value of my sorceproperty don't matter if its null or not. If i do the conversion outside on automapper it works fine.

Source/destination types

public class Source
{
    public byte[] Bytes { get; set; }
}

public class Destination
{
    public ByteString Bytes { get; set; }
}

Mapping configuration

var mapperConfiguration = new MapperConfiguration(cfg =>
{
    cfg.CreateMap<Source, Destination>();
    cfg.CreateMap<byte[], ByteString>().ConstructUsing(x => ByteArrayToByteString(x));
});

private ByteString ByteArrayToByteString(byte[] arg)
{
    return arg != null ? ByteString.CopyFrom(arg) : null;
}

Version: 10.1.1

Expected behavior

ByteString mapped with contents of byte[]

Actual behavior

Google.Protobuf.ByteString needs to have a constructor with 0 args or only optional args.

Steps to reproduce

var source = new Source(); 

mapper.Map<Destination>(source);

[jbogard]

You should be using ConvertUsing here, not ConstructUsing. ConstructUsing means "construct, then map" where ConvertUsing means "just use this to map and ignore anything else".

[schhwork]

Thast makes perfect sense actually. ConvertUsing was what i expected. Thank you, i took it from one of our other mappings and didnt realize this. My mistake, but thank you for giving me an answer even though this was an oversight be me.