in csharp/avro/src/KafkaAvroAsyncSerializer.cs [39:50]
public async Task<byte[]> SerializeAsync(T o, SerializationContext context)
{
if (o == null)
{
return null;
}
BinaryContent content = await serializer.SerializeAsync<BinaryContent, T>(o);
var schemaIdBytes = Encoding.UTF8.GetBytes(content.ContentType.ToString());
context.Headers.Add("content-type", schemaIdBytes);
return content.Data.ToArray();
}