Mapping FileHelpers to multiple output properties

Question

I'm using the C# FileHelpers library to efficiently parse large delimited files into validation objects.

However, I'd like to be able to map a single input file column to more than one output class property, but can't find an obvious way to achieve this. I've looked at ITransformable, but I don't want to map to yet another object to cut down on memory during the operation, and I've looked at the DynamicFieldBuilder/DynamicClassBuilder objects, but these seem to only allow me to describe what's in the input file, not what should be in the output instance.

I am trying to avoid having to load the file twice or do some kind of object-to-object mapping after the fact.

Input File Example:

ColumnA|ColumnB
Foo|Baz

Output Class Example:

public class FooBar
{
    public string ColumnA_One;
    public string ColumnA_Two;
    public string ColumnB_One;
    public string ColumnB_Two;
}

Answer 1

You can mark the duplicate columns with the FieldIgnored attribute and use the AfterReadRecord event to fill them.

class Program
{
    [DelimitedRecord("|")]
    public class FooBar
    {
        public string ColumnA_One;       
        [FieldIgnored]
        public string ColumnA_Two;        

        public string ColumnB_One;        
        [FieldIgnored]
        public string ColumnB_Two;
    }

    static void Main(string[] args)
    {
        FileHelperEngine engine = new FileHelperEngine(typeof(FooBar));
        engine.AfterReadRecord += engine_AfterReadRecord;
        FooBar[] records = engine.ReadFile("FileIn.txt") as FooBar[];
    }

    static void engine_AfterReadRecord(EngineBase engine, FileHelpers.Events.AfterReadEventArgs<object> e)
    {
        FooBar fooBar = e.Record as FooBar;
        fooBar.ColumnA_Two = fooBar.ColumnA_One;
        fooBar.ColumnB_Two = fooBar.ColumnB_One;
    }
}