c#中executereader執行查詢示例 轉

c#中executereader執行查詢示例

 

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

 

ExecuteReader執行查詢實例

ExecuteReader方法存在的目的只有一個：盡可能快地對數據庫進行查詢並得到結果。ExecuteReader 返回一個DataReader對象：如果在SqlCommand對象中調用，則返回SqlDataReader；如果在OleDbCommand對象中調用，返回的是OleDbDataReader。可以調用DataReader的方法和屬性迭代處理結果集。它是一個快速枚舉數據庫查詢結果的機制，是只讀、只進的。對SqlDataReader.Read的每次調用都會從結果集中返回一行。

 

復制代碼代碼如下:

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返回的對象類型是SqlDataReader
                    {
                           //Read是bool類型，初始指針指向第一條數據之前，每調用一次reader，指針就下移一條，只要沒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，因為查的是*，所以就和表中的列數一樣。
                            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 +"'";//字符串拼接查找數據庫。
                    cmd.CommandText = "select age from T_Student where name=@name or age>@age";//與數據庫進行數據對比。
                    //@參數:不能用來替換表名，字段名，select之類的關鍵字等。
                    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)中的參數是看cmd.CommandText中的查詢結果有幾個。
                            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);
                        }
                    }
                }
            }
        }
    }
}

 

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