c#取數據庫數據 ---兩種方法

通常有以下兩種方式 SqlDataReader 和SqlDataAdapter|DataSet方式
SqlDataReader 方式使用方式如下：
using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Text;  
using System.Data.SqlClient;  
  
namespace Login  
{  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            //新建一個數據庫連接  
            using(SqlConnection conn = new SqlConnection(GetConnectString()))  
            {  
                conn.Open();//打開數據庫  
                //Console.WriteLine("數據庫打開成功!");  
                //創建數據庫命令  
                SqlCommand cmd = conn.CreateCommand();  
                //創建查詢語句  
                cmd.CommandText = "SELECT * FROM userinfo";  
                //從數據庫中讀取數據流存入reader中  
                SqlDataReader reader = cmd.ExecuteReader();                 
                  
                //從reader中讀取下一行數據,如果沒有數據,reader.Read()返回flase  
                while (reader.Read())  
                {  
                    //reader.GetOrdinal("id")是得到ID所在列的index,  
                    //reader.GetInt32(int n)這是將第n列的數據以Int32的格式返回  
                    //reader.GetString(int n)這是將第n列的數據以string 格式返回  
                    int id = reader.GetInt32(reader.GetOrdinal("id"));  
                    string name = reader.GetString(reader.GetOrdinal("name"));  
                    string pwd = reader.GetString(reader.GetOrdinal("password"));  
                    int age = reader.GetInt32(reader.GetOrdinal("age"));  
                    string sex = reader.GetString(reader.GetOrdinal("sex"));  
                    string phone = reader.GetString(reader.GetOrdinal("phone"));  
                    string address = reader.GetString(reader.GetOrdinal("Address"));  
  
                    //格式輸出數據  
                    Console.Write("ID:{0},Name:{1},PWD:{2},Age:{3},Sex:{4},Phone{5},Address:{6}\n", id, name, pwd, age, sex, phone, address);  
                }  
            }  
            Console.ReadKey();  
        }  
        //得到一個數據庫連接字符串  
        static string GetConnectString()  
        {  
            return "Data Source=(local);Initial Catalog=db1;Integrated Security=SSPI;";  
        }  
    }  
}  
SqlDataAdapter|DataSet 方式如下
加入為SQLSERVER數據庫：
using System.Data.SqlClient;
using System.Data;
 SqlConnection conn = new SqlConnection(connectionString);
            SqlCommand cmd = new SqlCommand("secelt * from userinfo", conn);
            SqlDataAdapter sda = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();
            sda.Fill(ds, "table");
            return ds.Tables["table"];//返回的是一個DataTable