Using external classes/variables with CustomTypeConverter

Question

I need to convert a double field into a custom string output depending on a mapped class' parameter. This is most easily shown with code.

public enum Type {
    Mod,
    NonMod
}

public class Document {
    public double Value { get; set; }
    public Type DocType { get; set; }
}

---

Now attempting to convert the Value field...

public class DocumentMap : ClassMap<Document>
{
    public DocumentMap
    {
        Map(m => m.Value).Index(0).Name("Value").TypeConverter<CustomDoubleConverter>()
        Map(m => m.Type).Index(1).Name("Type");
    }

    private class CustomDoubleConverter : DefaultTypeConverter
    {
        public override object ConvertFromString(string text, IReaderRow row, MemberMapData memberMapData)
        {
            return text == "ModVal" ? null : double.Parse(text);
        }
        public override string ConvertToString(object value, IWriterRow row, MemberMapData memberMapData)
        {
            return (double)value == 0 /* && Document.Type == Type.Mod*/ ? "ModVal" : value.ToString();
        }
    }
}

I would need the Document type within CustomDoubleConverter to write "ModVal" only for Mod type documents. The only issue is converting the value to a string as converting back would mean it was properly delineated initially. I would need to know the document types for each of the documents, so I don't believe a parameter could be passed into the DocumentMap instantiation as it is only instantiated once.

Answer 1

I'm not quite sure I understand all of your logic, but I think Convert could work for you in the ClassMap.

public class DocumentMap : ClassMap<Document>
{
    public DocumentMap()
    {
        Map(m => m.Value).Name("Value")
        .Convert(args =>
        {
            var value = args.Row.GetField<string>(0);
            
            return value == "ModVal" ? 0 : double.Parse(value);

        }).Convert(args =>
        {
            return args.Value.Value == 0 && args.Value.DocType == Type.Mod ? "ModVal" : args.Value.Value.ToString();
        });
        Map(m => m.DocType).Index(1).Name("Type");
    }
}