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ExecuteReader履行查詢實例
ExecuteReader辦法存在的目標只要一個：盡量快地對數據庫停止查詢並獲得成果。ExecuteReader 前往一個DataReader對象：假如在SqlCommand對象中挪用，則前往SqlDataReader；假如在OleDbCommand對象中挪用，前往的是OleDbDataReader。可以挪用DataReader的辦法和屬性迭代處置成果集。它是一個疾速列舉數據庫查詢成果的機制，是只讀、只進的。對SqlDataReader.Read的每次挪用都邑從成果集中前往一行。
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履行查詢
{
/// <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前往的對象類型是SqlDataReader
{
//Read是bool類型，初始指針指向第一條數據之前，每挪用一次reader，指針就下移一條，只需沒有移到最初一條以後，就前往true。
while (reader.Read())
{
string name = reader.GetString(1);//GetString(1)獲得表中第一列的值，用name吸收，由於查的是*，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";//與數據庫停止數據比較。
//@參數:不克不及用來調換表名，字段名，select之類的症結字等。
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取得的是int類型
//GetInt64取得的是long類型（bigint）
int age = reader.GetInt32(0);//GetInt32(0)中的參數是看cmd.CommandText中的查詢成果有幾個。
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);
}
}
}
}
}
}
}
