c#中executereader執(zhí)行查詢示例分享

更新時(shí)間：2014年04月02日 10:33:40 作者：

這篇文章主要介紹了c#中executereader執(zhí)行查詢示例,需要的朋友可以參考下

ExecuteReader執(zhí)行查詢實(shí)例

ExecuteReader方法存在的目的只有一個(gè)：盡可能快地對(duì)數(shù)據(jù)庫(kù)進(jìn)行查詢并得到結(jié)果。ExecuteReader 返回一個(gè)DataReader對(duì)象：如果在SqlCommand對(duì)象中調(diào)用，則返回SqlDataReader；如果在OleDbCommand對(duì)象中調(diào)用，返回的是OleDbDataReader?？梢哉{(diào)用DataReader的方法和屬性迭代處理結(jié)果集。它是一個(gè)快速枚舉數(shù)據(jù)庫(kù)查詢結(jié)果的機(jī)制，是只讀、只進(jìn)的。對(duì)SqlDataReader.Read的每次調(diào)用都會(huì)從結(jié)果集中返回一行。

復(fù)制代碼代碼如下:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Data.SqlClient;

namespace ExecuteReader執(zhí)行查詢
{
    /// <summary>
    /// Window1.xaml 的交互邏輯
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            using (SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=MyTest;User Id=sa;Password=123;"))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "select * from T_Student where Age<100";
                    using (SqlDataReader reader = cmd.ExecuteReader())//ExecuteReader返回的對(duì)象類型是SqlDataReader
                    {
                           //Read是bool類型，初始指針指向第一條數(shù)據(jù)之前，每調(diào)用一次reader，指針就下移一條，只要沒(méi)有移到最后一條之后，就返回true。
                        while (reader.Read())
                        {
                            string name = reader.GetString(1);//GetString(1)得到表中第一列的值，用name接收，因?yàn)椴榈氖?，所以就和表中的列數(shù)一樣。
                            int age = reader.GetInt32(2);
                            MessageBox.Show(name+","+age);
                        }
                    }
                }
            }
        }

        private void btnQuery_Click(object sender, RoutedEventArgs e)
        {
            using (SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=MyTest;User Id=sa;Password=123;"))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    //cmd.CommandText = "select age from T_Student where name='"+ txtName.Text +"'";//字符串拼接查找數(shù)據(jù)庫(kù)。
                    cmd.CommandText = "select age from T_Student where name=@name or age>@age";//與數(shù)據(jù)庫(kù)進(jìn)行數(shù)據(jù)對(duì)比。
                    //@參數(shù):不能用來(lái)替換表名，字段名，select之類的關(guān)鍵字等。
                    cmd.Parameters.Add(new SqlParameter("@name",txtName.Text));
                    cmd.Parameters.Add(new SqlParameter("@age",Convert.ToInt32(txtAge.Text)));
                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            //GetInt32獲得的是int類型
                            //GetInt64獲得的是long類型（bigint）
                            int age = reader.GetInt32(0);//GetInt32(0)中的參數(shù)是看cmd.CommandText中的查詢結(jié)果有幾個(gè)。
                            MessageBox.Show(age.ToString());
                        }
                    }
                }
            }
        }

        private void btnHobby_Click(object sender, RoutedEventArgs e)
        {
            using (SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=MyTest;User Id=sa;Password=123;"))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "select * from T_Student where name like '張%'";
                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            string hobby = reader.GetString(3);
                            MessageBox.Show(hobby);
                        }
                    }
                }
            }
        }

        private void btnQuery1_Click(object sender, RoutedEventArgs e)
        {
            using (SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=MyTest;User Id=sa;Password=123;"))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "select hobbit from T_Student where age>@age or hobbit =@hobbit";
                    cmd.Parameters.Add(new SqlParameter("@age", txtAge1.Text));
                    cmd.Parameters.Add(new SqlParameter("@hobbit",txtHobby.Text));
                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            string str = reader.GetString(0);
                            MessageBox.Show(str);
                        }
                    }
                }
            }
        }
    }
}