Conditionally Ignore reference mapping

Question

Is it possible to programatically/dynamically ignore a reference mapping if it satisfies a certain condition?

Consider the following structure

public class SkuDto
{
    public string Name;
    public InnerSkuDto InnerSku;
}

public class InnerSkuDto
{
    public Guid SkuNumber;
}

public sealed class SkuMap : ClassMap<SkuDto>
{
    Map(m => m.Name);
    References<InnerSkuMap>(m => m.InnerSku);
}

public sealed class InnerSkuMap : ClassMap<InnerSkuDto> { ... }

Now sometimes the InnerSku property in the SkuDto object can be null in which case the resulting CSV output contains 00000000-0000-0000-0000-000000000000 for the SkuNumber instead of an empty cell. So is it possible to ignore the InnerSku if its null?

Answer 1

A Guid can't be null, so it defaults to an empty Guid, which you see in the CSV output. One solution is to change SkuNumber to a nullable Guid

public class InnerSkuDto
{
    public Guid? SkuNumber;
}

If you can't or don't want to change SkuNumber to a nullable Guid, the other option is to use a custom converter. Here I override the ConvertToString method of GuidConverter.

public class EmptyGuidConverter : GuidConverter
{
    public override string ConvertToString(object value, IWriterRow row, MemberMapData memberMapData)
    {
        if ((Guid)value == Guid.Empty)
        {
            return string.Empty;
        }

        return base.ConvertToString(value, row, memberMapData);
    }
}

public sealed class InnerSkuMap : ClassMap<InnerSkuDto>
{
    public InnerSkuMap()
    {
        Map(m => m.SkuNumber).TypeConverter<EmptyGuidConverter>();
    }
}

Or instead of registering the converter for a single property, you can register it with your CsvWriter for all Guid values. Just make sure to add it before registering your ClassMap.

csv.Configuration.TypeConverterCache.AddConverter<Guid>(new EmptyGuidConverter());