Sample sharing of executereader execution queries in c

ExecuteReader executes the query instance

The ExecuteReader method exists for one reason only: to query the database as quickly as possible and get results. ExecuteReader returns 1 DataReader object: SqlDataReader if called in an SqlCommand object; If invoked in an OleDbCommand object, OleDbDataReader is returned. You can call DataReader's methods and properties to iterate over the result set. It is a quick enumeration of database query results mechanism, is read-only, only in. Each call to SqlDataReader.Read returns 1 row from the result set.

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 Execute the query 
{
    /// <summary>
    /// Window1.xaml  Interaction logic of 
    /// </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 The returned object type is SqlDataReader
                    {
                           //Read is bool Type, with an initial pointer to a 1 A piece of data before each call 1 time reader And the pointer goes down 1 Bar, as long as it doesn't move to the end 1 After the bar, it returns true . 
                        while (reader.Read())
                        {
                            string name = reader.GetString(1);//GetString(1) You get the number in the table 1 The value of the column name Yes, because it's looking up * And the number of columns in the table 1 The sample. 
                            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 +"'";// String concatenation finds the database. 
                    cmd.CommandText = "select age from T_Student where name=@name or age>@age";// Compare the data with the database. 
                    //@ parameter : Cannot be used to replace table names, field names, select Keyword, etc. 
                    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 Is obtained by int type 
                            //GetInt64 Is obtained by long Type ( bigint ) 
                            int age = reader.GetInt32(0);//GetInt32(0) The parameter is look cmd.CommandText There are several query results in. 
                            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 ' zhang %'";
                    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);
                        }
                    }
                }
            }
        }
    }
}