使用ExecuteReader读取多行多列的数据

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace ADO.NET详解
{
    class Program
    {
        static void Main(string[] args)
        {

      using (SqlConnection conn = new SqlConnection(@"Data Source=.;Database=Database1;user ID=sa;pwd=888888"))//在Sqlconnection,Sqlcommand,SqlDataReader等使用using，能够
            //释放掉所占用的资源，至关于Disposed()方法.
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "select * from T_Users";
                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        Console.WriteLine("数据库中有如下用户名:");
                        while (reader.Read()) //循环读取数据库中的数据，直到最后一条记录的最后
                        { 
                                                      //这里须要指定某列的序号
                            //Console.WriteLine(reader.GetString(1));

                            //而使用下列的方法GetOrdinal能够直接指定某列的名称，而不用把列序号写死在程序里，跟以上效果同样
                            Console.WriteLine(reader.GetString(reader.GetOrdinal("username")));
                        }
                    }

                }
                Console.ReadKey();
            }
        }
    }
}

 运行效果：

数据库数据：