Microsoft Jet OLE DB Providerを使ってCSVファイルを読み込んだときのDataTypeについて

private void button4_Click(object sender, EventArgs e)
{
    string dir = "C:\\TEMP";
    string fname = "a2z.csv";
    string constr = string.Format(
        @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0};Extended Properties=""Text;HDR=Yes;FMT=Delimited""",
        dir);
    OleDbConnection con = new OleDbConnection(constr);
    con.Open();
    string sql = string.Format(
        "SELECT * FROM [{0}]", fname);
    OleDbCommand cmd = new OleDbCommand(sql, con);
    OleDbDataReader reader = cmd.ExecuteReader(CommandBehavior.SequentialAccess);
    try
    {
        DataTable dt = reader.GetSchemaTable();
        dataGridView1.DataSource = dt;
    }
    catch (Exception)
    {}
    finally
    {
        con.Close();
        reader.Close();
        reader.Dispose();
    }
}