ExcelReaderEngine

using System;
using System.Collections.Generic;
using System.Linq;
using System.Data.OleDb;
using System.Reflection;

namespace Sync.Core
{
    public class ExcelReaderEngine<T> where T: class, new()
    {
        private const string JET_CONNECTION_STRING =
            "Provider=Microsoft.Jet.OLEDB.4.0;Data source={0};Extended Properties=Excel 8.0;;Extended Properties=\"Excel 12.0;HDR=YES;IMEX=1;MaxScanRows=0;\"";
        private const string ACE_CONNECTION_STRING =
            "Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=\"Excel 12.0;HDR=YES;IMEX=1;MaxScanRows=0;\"";
        private const string SELECT_STATEMENT = "SELECT * FROM [{0}$]";

        IEnumerable<FieldInfo> _fields = null;

        public ExcelReaderEngine()
        {
            _fields = typeof(T).GetFields(BindingFlags.Instance | BindingFlags.Public).OrderBy(i => i.MetadataToken);
        }

        public IEnumerable<T> ReadData(OleDbConnection conn, OleDbCommand comm)
        {
            List<T> result = new List<T>();
            var reader = comm.ExecuteReader();
            while (reader.Read())
            {
                var index = 0;
                var entity = new T();
                foreach (var field in _fields)
                {
                    var value = reader.GetValue(index);
                    if (value is DBNull) { value = null; }
                    index++;

                    if (field.FieldType == typeof(String))
                    {
                        field.SetValue(entity, value);
                    }
                    else if (field.FieldType == typeof(Int32))
                    {
                        field.SetValue(entity, value != null ? Int32.Parse(value.ToString()) : 0);
                    }
                    else if (field.FieldType == typeof(Double))
                    {
                        field.SetValue(entity, value != null ? Double.Parse(value.ToString()) : 0.0);
                    }
                    else if (field.FieldType == typeof(DateTime))
                    {
                        field.SetValue(entity, value != null ? DateTime.Parse(value.ToString()) : new DateTime());
                    }
                }
                result.Add(entity);
            }
            return result;
        }

        /// <summary>
        /// Returns OPENED connection to Excel file.
        /// </summary>
        /// <param name="file">File name</param>
        /// <returns>Connection</returns>
        private OleDbConnection Connect(string file)
        {
            OleDbConnection result = null;
            // This doesn't look so nice. But it's the only way to leap over MS Excel driver problems.
            try
            {
                result = new OleDbConnection(String.Format(ACE_CONNECTION_STRING, file));
                result.Open();
            }
            catch
            {
                try
                {
                    result = new OleDbConnection(String.Format(JET_CONNECTION_STRING, file));
                    result.Open();
                }
                catch
                {
                    throw;
                }
            }
            return result;
        }

        public IEnumerable<T> GetData(string file, string page)
        {
            using (var conn = Connect(file))
            {
                using (var comm = conn.CreateCommand())
                {
                    comm.CommandText = String.Format(SELECT_STATEMENT, page);
                    return ReadData(conn, comm);
                }
            }
        }
    }
}