ExecuteReader执行查询实例

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执行查询

{

/// <summary>

/// Window1.xaml 的交互逻辑

/// </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返回的对象类型是SqlDataReader

{

//Read是bool类型，初始指针指向第一条数据之前，每调用一次reader，指针就下移一条，只要没有移到最后一条之后，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，因为查的是*，所以就和表中的列数一样。

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 +"'";//字符串拼接查找数据库。

cmd.CommandText = "select age from T_Student where name=@name or age>@age";//与数据库进行数据对比。

//@参数:不能用来替换表名，字段名，select之类的关键字等。

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获得的是int类型

//GetInt64获得的是long类型（bigint）

int age = reader.GetInt32(0);//GetInt32(0)中的参数是看cmd.CommandText中的查询结果有几个。

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 '张%'";

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);

}

}

}

}

}

}

}