Filehelpers and Entity Framework

Question

I'm using Filehelpers to parse a very wide, fixed format file and want to be able to take the resulting object and load it into a DB using EF. I'm getting a missing key error when I try to load the object into the DB and when I try and add an Id I get a Filehelpers error. So it seems like either fix breaks the other. I know I can map a Filehelpers object to a POCO object and load that but I'm dealing with dozens (sometimes hundreds of columns) so I would rather not have to go through that hassle.

I'm also open to other suggestions for parsing a fixed width file and loading the results into a DB. One option of course is to use an ETL tool but I'd rather do this in code.

Thanks!

---

This is the FileHelpers class:

public class AccountBalanceDetail
{
    [FieldHidden]
    public int Id;  // Added to try and get EF to work

    [FieldFixedLength(1)]
    public string RecordNuber;

    [FieldFixedLength(3)]
    public string Branch;
    // Additional fields below
}

And this is the method that's processing the file:

public static bool ProcessFile()
{
    var dir = Properties.Settings.Default.DataDirectory;

    var engine = new MultiRecordEngine(typeof(AccountBalanceHeader), typeof(AccountBalanceDetail), typeof(AccountBalanceTrailer));
    engine.RecordSelector = new RecordTypeSelector(CustomSelector);

    var fileName = dir + "\\MOCK_ACCTBAL_L1500.txt";

    var res = engine.ReadFile(fileName);

    foreach (var rec in res)
    {
        var type = rec.GetType();
        if (type.Name == "AccountBalanceHeader") continue;
        if (type.Name == "AccountBalanceTrailer") continue;
        var data = rec as AccountBalanceDetail;  // Throws an error if AccountBalanceDetail.Id has a getter and setter 


        using (var ctx = new ApplicationDbContext())
        {
            // Throws an error if there is no valid Id on AccountBalanceDetail 
            // EntityType 'AccountBalanceDetail' has no key defined. Define the key for this EntityType.
            ctx.AccountBalanceDetails.Add(data);  
            ctx.SaveChanges();
        }

        //Console.WriteLine(rec.ToString());

    }

    return true;
}

Answer 1

Entity Framework needs the key to be a property, not a field, so you could try declaring it instead as:

public int Id {get; set;}

I suspect FileHelpers might well be confused by the autogenerated backing field, so you might need to do it long form in order to be able to mark the backing field with the [FieldHidden] attribute, i.e.,

[FieldHidden]
private int _Id;
public int Id
{
   get { return _Id; }
   set { _Id = value; }
}

However, you are trying to use the same class for two unrelated purposes and this is generally bad design. On the one hand AccountBalanceDetail is the spec for the import format. On the other you are also trying to use it to describe the Entity. Instead you should create separate classes and map between the two with a LINQ function or a library like AutoMapper.