FileHelpers dynamic fixed field positions

This is what i did. Hope it may help you.

1. Created DB table and stored the different Fixed File layout formats (like Field Name size, Data Type and Length of the field etc...)
2. In UI first user selects the Fixed File Layout and then selects the Fixed File to import.
3. Based on selected Layout i create Fixed length Type class at run time using the below code.

private void ImportFiles()
{
    DataTable dt = GetFixedFileSpecsFromDB(layoutName); //Get the specs
    //Create Dynamic class based on Specs above
    FixedLengthClassBuilder cb = GetSpecClass(dt);
    //Create FileHelpers engine instance
    FileHelperEngine engine = new FileHelperEngine(cb.CreateRecordClass());
    //Read file data into Data table
    DataTable dtImportData = engine.ReadFileAsDT(ImportFilePath);
}

//Method to create the Fixed lentgh dynamic class
 public static FixedLengthClassBuilder GetSpecClass(DataTable dt)
    {

        string className = "ImportSpecifications";
        FixedLengthClassBuilder cb = new FixedLengthClassBuilder(className);
        //Loop thru each field and prepare the class
        foreach (DataRow dr in dt.Rows)
        {
            int fieldLength = Convert.ToInt32(dr.Field<decimal>("FieldLength"));
            switch (dr["FieldDataType"].ToString())
            {
                case "String":
                    cb.AddField(dr.Field<string>("FieldName"), fieldLength, typeof(string));
                    cb.LastField.FieldNullValue = string.Empty;
                    cb.LastField.TrimMode = FileHelpers.TrimMode.Both;
                    break;
                case "Date":
                    cb.AddField(dr.Field<string>("FieldName"), fieldLength, typeof(DateTime));
                    cb.LastField.FieldNullValue = string.Empty;
                    break;
                case "Integer":
                    cb.AddField(dr.Field<string>("FieldName"), fieldLength, typeof(int?));
                    //cb.LastField.FieldNullValue = 0;
                    break;
                case "Long Integer":
                    cb.AddField(dr.Field<string>("FieldName"), fieldLength, typeof(long));
                    cb.LastField.FieldNullValue = 0;
                    break;
                case "Decimal":
                    cb.AddField(dr.Field<string>("FieldName"), fieldLength, typeof(decimal?));
                    //cb.LastField.FieldNullValue = 0;
                    break;
                default:
                    break;
            }
        }
        return cb;
    }