How to return fully populated objects using FileHelpers for partially complete data?

问题

Assume you have a CSV file with the following structure

 LINE1:  ID,Description,Value
 LINE2:  1,Product1,2
 LINE3:  ,,3
 LINE4:  ,,4
 LINE5:  2,Product2,2
 LINE6:  ,,3
 LINE7:  ,,5

With the corresponding FileHelpers definition class

[DelimitedRecord(",") ]
[IgnoreFirst(1)] 
public class Product
{
    public int ID { get; set; }
    public string Description { get; set; }

    [FieldConverter(ConverterKind.Decimal)]
    public decimal Val{ get; set; }
}

How do use FileHelpers, to return objects such that each object is fully populated?

Let me clarify, currently, result of using engine.ReadFile will only produce objects from Lines 2 and 5 as fully populated, which makes sense since the fields are blank. However, objects from Lines 3 and 4 should also have the same ID and Description as Line 1. The Value field should remain untouched for each line. I am not sure what the correct term for the data is, but it seems to 'partially normalised'.

My current approach to solve this is as follows using the AfterRead event. I do not have a good grasp of Events, Event Handlers, delegates etc, so I am looking for an alternative way to achieve this using FileHelpers. It also seems very clunky.

    // call the csv repo using the ffg lines within a console app
    var repo2 = new CSVRepositoryBase<Product>();
    repo2.AfterRead +=new AfterReadHandler<object>(repo2_AfterRead);
    var products = repo2.Read("some file path");

    public static Product PreviousRecord { get; set; }

    private static void repo2_AfterRead
        (EngineBase engine, FileHelpers.Events.AfterReadEventArgs<object> e)
    {
        var record = (Product)e.Record;

        if (PreviousRecord == null)
        {
            PreviousRecord = new Product();
            PreviousRecord.ID = record.ID;
        }

        if (String.IsNullOrEmpty(record.ID)) // newline record = blank row
        {
            record.ID = PreviousRecord.ID;
        } 
        PreviousRecord.ID = record.ID;

    }


public class CSVRepositoryBase<T> where T : class
{
    // shorten for brevity 

    public IEnumerable<T> Read(string fileName){/*snip*/ }

    #region Events
    public event AfterReadHandler<object> AfterRead
    {
        add { engine.AfterReadRecord += value; }
        remove { engine.AfterReadRecord -= value; }
    }
    #endregion 
}

回答1:

You can try using the interfaces for AfterRead instead of events like this.

If I understand right you need to do something like that:

[DelimitedRecord(",") ]
[IgnoreFirst(1)] 
public class Product
:INotifyRead
{
    public int? ID;
    public string Description;

    [FieldConverter(ConverterKind.Decimal)]
    public decimal? Val;

    private static Product Previuous;

    public void AfterRead(EngineBase engine, string line)
    {
        if (!ID.HasValue && Previous != null)
              this.ID = Previus.ID;

        if (!Val.HasValue && Previous != null)
              this.Val= Previus.Val;

        Previuous = this;
    }
}

Hope this helps

来源：https://stackoverflow.com/questions/3923847/how-to-return-fully-populated-objects-using-filehelpers-for-partially-complete-d

标签

.net

csv

filehelpers