ACCP C#Windows 第三章课后5

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using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;using System.Data.SqlClient;namespace a{        public partial class Form2 : Form    {        public Form2()        {            InitializeComponent();        }        private void button1_Click(object sender, EventArgs e)        {            flv();        }        private void flv()        {            if (listView1.Items.Count > 0)            {                listView1.Items.Clear();            }            StringBuilder sql = new StringBuilder();            sql.AppendLine("select name,type,number,price from shop");            sql.AppendFormat("where type like '%{0}%'", this.comboBox1.Text.Trim());            DBHelper d = new DBHelper();            try            {                SqlCommand com = new SqlCommand(sql.ToString(), d.Connection);                d.OpenConnection();                SqlDataReader r = com.ExecuteReader();                if (!r.HasRows)                {                    MessageBox.Show("没有要查找的记录!", "CAPTION", MessageBoxButtons.OK, MessageBoxIcon.Information);                }                else                {                    while (r.Read())                    {                        string no = r["name"].ToString();                        string name = r["type"].ToString();                        string gender = r["number"].ToString();                        string gradename = r["price"].ToString();                        ListViewItem i = new ListViewItem(no);                        i.SubItems.Add(name);                        i.SubItems.Add(gender);                        i.SubItems.Add(gradename);                        listView1.Items.Add(i);                    }                }                r.Close();            }            catch (Exception ex)            {                MessageBox.Show("系统出现错误!", "CAPTION", MessageBoxButtons.OK, MessageBoxIcon.Error);            }            finally            {                d.CloseConnection();            }        }        private void Form2_Load(object sender, EventArgs e)        {        }    }    public class DBHelper    {        // 数据库连接字符串        private string connString = @"Data Source=.;Initial Catalog=MySchool;Integrated Security=True";        // 数据库连接 Connection 对象        private SqlConnection connection;        /// <summary>        /// Connection对象        /// </summary>        public SqlConnection Connection        {            get            {                if (connection == null)                {                    connection = new SqlConnection(connString);                }                return connection;            }        }        /// <summary>        /// 打开数据库连接        /// </summary>        public void OpenConnection()        {            if (Connection.State == ConnectionState.Closed)            {                Connection.Open();            }            else if (Connection.State == ConnectionState.Broken)            {                Connection.Close();                Connection.Open();            }        }        /// <summary>        /// 关闭数据库连接        /// </summary>        public void CloseConnection()        {            if (Connection.State == ConnectionState.Open || Connection.State == ConnectionState.Broken)            {                Connection.Close();            }        }    }}
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