B.
测试实例
说明
1. 此测试，直接使用 ASP.NET（似乎不影响对比性），抱歉了，偶就会 WebForm，比较理想的当然整个 Console Applilcation 让她跑

2. 懒于准备样表数据，直接使用 SQL Server 2k. Northwind.Products 表，且只读取 ProductID 字段（INT 型），并由应用程序多次重复读取同一数据，模拟大数据量的效果

测试代码

protected void Button1_Click(object sender, EventArgs e)
    {
        int i = 5;
        while (i-- > 0) {
            ExecuteTest();
            System.Threading.Thread.Sleep(1000 * 10);
        }
    }

    private void ExecuteTest()
    {
        const int COLUMN_INDEX_PRODUCT_ID = 0;
        const string COLUMN_NAME_PRODUCT_ID = "ProductID";

        StringBuilder sb = new StringBuilder();
        int loops = 100;
        for (int k = 0; k < 5; k++, loops *= 10) {
            sb.AppendFormat("{0, 10:N0}\t", loops * 50);

            // 1. DataReader.GetXXX(<<ColumnIndex>>)
            using (SqlDataReader dr = GetDataReader()) {
                int productId, i;
                DateTime start = DateTime.Now;
                while (dr.Read()) {
                    i = loops;
                    while (i-- > 0) {
                        productId = dr.GetInt32(COLUMN_INDEX_PRODUCT_ID);
                    }
                }
                DateTime end = DateTime.Now;
                TimeSpan span = end - start;
                sb.Append(span.TotalSeconds.ToString("f7")).Append("\t");
            }

            // 2. (<<Type>>)DataReader[<<ColumnIndex>>]
            using (SqlDataReader dr = GetDataReader()) {
                int productId, i;
                DateTime start = DateTime.Now;
                while (dr.Read()) {
                    i = loops;
                    while (i-- > 0) {
                        productId = (int)dr[COLUMN_INDEX_PRODUCT_ID];
                    }
                }
                DateTime end = DateTime.Now;
                TimeSpan span = end - start;
                sb.Append(span.TotalSeconds.ToString("f7")).Append("\t");
            }

            // 3. Convert.ToXXX(DataReader[<<ColumnIndex>>])
            using (SqlDataReader dr = GetDataReader()) {
                int productId, i;
                DateTime start = DateTime.Now;
                while (dr.Read()) {
                    i = loops;
                    while (i-- > 0) {
                        productId = Convert.ToInt32(dr[0]);
                    }
                }
                DateTime end = DateTime.Now;
                TimeSpan span = end - start;
                sb.Append(span.TotalSeconds.ToString("f7")).Append("\t");
            }

            // 4. (<<Type>>)DataReader[<<ColumnName>>]
            using (SqlDataReader dr = GetDataReader()) {
                int productId, i;
                DateTime start = DateTime.Now;
                while (dr.Read()) {
                    i = loops;
                    while (i-- > 0) {
                        productId = (int)dr[COLUMN_NAME_PRODUCT_ID];
                    }
                }
                DateTime end = DateTime.Now;
                TimeSpan span = end - start;
                sb.Append(span.TotalSeconds.ToString("f7")).Append("\t");
            }

            // 5. Convert.ToXXX(DataReader[<<ColumnName>>]
            using (SqlDataReader dr = GetDataReader()) {
                int productId, i;
                DateTime start = DateTime.Now;
                while (dr.Read()) {
                    i = loops;
                    while (i-- > 0) {
                        productId = Convert.ToInt32(dr[COLUMN_NAME_PRODUCT_ID]);
                    }
                }
                DateTime end = DateTime.Now;
                TimeSpan span = end - start;
                sb.Append(span.TotalSeconds.ToString("f7")).Append("\t");
            }

            // 6. DataReader.GetXXX(DataReader.GetOrdinal(<<ColumnName>>))
            using (SqlDataReader dr = GetDataReader()) {
                int productId, i;
                DateTime start = DateTime.Now;
                while (dr.Read()) {
                    i = loops;
                    while (i-- > 0) {
                        productId = dr.GetInt32(dr.GetOrdinal(COLUMN_NAME_PRODUCT_ID));
                    }
                }
                DateTime end = DateTime.Now;
                TimeSpan span = end - start;
                sb.Append(span.TotalSeconds.ToString("f7")).Append("\t");
            }

            // 7. DataReader.GetXXX((Int32)Hashtable[<<ColumnName>>])
            //    Hashtable.Add(<<ColumnName>>, DataReader.GetOrdinal(<<ColumnName>>))
            using (SqlDataReader dr = GetDataReader()) {
                int productId, i;
                DateTime start = DateTime.Now;
                Hashtable columns = new Hashtable();

                int j = 0;
                while (dr.Read()) {
                    i = loops;
                    while (i-- > 0) {
                        if (j++ == 0) columns.Add(COLUMN_NAME_PRODUCT_ID, dr.GetOrdinal("ProductID"));
                        productId = dr.GetInt32((int)columns[COLUMN_NAME_PRODUCT_ID]);
                    }
                }
                DateTime end = DateTime.Now;
                TimeSpan span = end - start;
                sb.Append(span.TotalSeconds.ToString("f7")).Append("\t");
            }

            // 8. DataReader.GetXXX(Dictionary<string, int>[<<ColumnName>>])
            //    Dictionary<string, int>.Add(<<ColumnName>>, DataReader.GetOrdinal(<<ColumnName>>))
            using (SqlDataReader dr = GetDataReader()) {
                int productId, i;
                DateTime start = DateTime.Now;
                Dictionary<string, int> columns = new Dictionary<string, int>();
                int j = 0;
                while (dr.Read()) {
                    i = loops;
                    while (i-- > 0) {
                        if (j++ == 0) columns.Add(COLUMN_NAME_PRODUCT_ID, dr.GetOrdinal("ProductID"));
                        productId = dr.GetInt32(columns[COLUMN_NAME_PRODUCT_ID]);
                    }
                }
                DateTime end = DateTime.Now;
                TimeSpan span = end - start;
                sb.Append(span.TotalSeconds.ToString("f7")).Append("\t");
            }

            sb.AppendLine();
        }
        sb.AppendLine();

        string path = Server.MapPath("result.txt");
        File.AppendAllText(path, sb.ToString());
    }
   
    private SqlDataReader GetDataReader()
    {
        string connStr = "server=.;database=Northwind;uid=sa;";
        SqlConnection conn = new SqlConnection(connStr);
        SqlCommand cmd = conn.CreateCommand();
        cmd.CommandText = "SELECT TOP 50 ProductID FROM Products";
        conn.Open();
        return cmd.ExecuteReader(CommandBehavior.CloseConnection);
    }