OleDB not supported in 64bit mode?

The main problem is that the Jet DBMS is a 32bit library that gets loaded into the calling process, so you will never be able to use Jet directly from within your app in 64bit mode. As Tim mentioned you could write your own csv parser, but since this is a shrink-wrap app you want something that will handle a wider range of formats. Luckily, there are a number of ways to talk 32-bit apps, so you can still use Jet with a trick.

I would write a little exe that was marked to run only in 32-bit mode. This exe would take a command line argument of the name of the file to read and the name of a temp file to write to. I would use Jet to load the csv/xls, then put the data into an array of arrays, and use the xml serializer to write the data to the temp file.

Then when I need to load/convert a csv/xls file, I would do the following:

object[][] ConvertFile(string csvOrXlsFile)
{
    var output = System.IO.Path.GetTempFileName();
    try
    {
        var startinfo = new System.Diagnostics.ProcessStartInfo("convert.exe",
            string.Format("\"{0}\" \"{1}\"", csvOrXlsFile, output));

        System.Diagnostics.Process proc = new System.Diagnostics.Process();
        proc.StartInfo = startinfo;

        proc.Start();
        proc.WaitForExit();

        var serializer = new System.Xml.Serialization.XmlSerializer(typeof(object[][]));
        using (var reader = System.IO.File.OpenText(output))
            return (object[][])serializer.Deserialize(reader);
    }
    finally
    {
        if (System.IO.File.Exists(output))
            System.IO.File.Delete(output);
    }
}

SpreadsheetGear for .NET can read and write .csv / .xls / .xlsx workbooks (and more) and supports 64 bit .NET 2.0+. SpreadsheetGear can be distributed royalty free with your shrink wrap applications.

You did not specify whether your application is WinForms or ASP.NET but SpreadsheetGear works with either. You can see live ASP.NET (C# & VB) samples here, learn about the WinForms samples here and download a free trial here if you want to try it yourself.

Disclaimer: I own SpreadsheetGear LLC

Actually I think Linq is your best solution for this.

Something like....

IEnumerable<MyObj> ObjList = GetObjList(yourCSVFileNAme);

var qry = from o in ObjList
          where o.MyField == Something
          select o;

and your GetObjList method looks something like

Public IEnumerable<MyObj> GetObjList(string filename)
{
  // Obvioulsly you would have some actual validation and error handling
  foreach(string line in File.ReadAllLines(filename))
  {
    string[] fields = line.Split(new char[]{','});
    MyObj obj = new MyObj();
    obj.Field = fields[0];
    obj.AnotherField = int32.Parse(fields[1]);
    yield return obj;
  }
}