C#开发数据库第三章课后题5

来源：互联网发布：约束最优化问题求解编辑：程序博客网时间：2024/06/05 22:32
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Data.SqlClient;using System.Data;namespace WindowsFormsApplication2{    class DBHelper    {        private string connString = @"Data Source=.;Initial Catalog=GoodsMenu;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();            }        }    }}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 WindowsFormsApplication2{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();        }        private void Form1_Load(object sender, EventArgs e)        {            comboBox1.Items.Add("请选择");            comboBox1.SelectedIndex = 0;            BindGrade();            AddGoods();        }        DBHelper db = new DBHelper();        public string CAPTION = "提示输入";        public bool BindGrade()        {            try            {                string sql = "SELECT * FROM  type";                db.OpenConnection();                SqlCommand comm = new SqlCommand(sql, db.Connection);                SqlDataReader myReader = comm.ExecuteReader();                while (myReader.Read())                {                    string type = myReader["Type"].ToString();                    this.comboBox1.Items.Add(type);                }                myReader.Close();                return true;            }            catch (Exception)            {                MessageBox.Show("系统发生错误!", CAPTION, MessageBoxButtons.OK, MessageBoxIcon.Warning);                return false;            }            finally            {                db.CloseConnection();            }        }                public void AddGoods()        {            string strsql = ("SELECT  [Name],[Type],[Number],[Price] FROM [Godds]");            try            {                SqlCommand comm = new SqlCommand(strsql, db.Connection);                db.OpenConnection();                SqlDataReader reader = comm.ExecuteReader();                while (reader.Read())                {                    string Type = reader["Type"].ToString();                    string Name = reader["Name"].ToString();                    int number = Convert.ToInt32(reader["Number"]);                    int price= Convert.ToInt32(reader["Price"]);                    ListViewItem item = new ListViewItem(Name);                    item.SubItems.AddRange(new string[] { Type, number.ToString(), price.ToString() });                    this.listView1.Items.Add(item);                }                reader.Close();            }            catch (Exception ex)            {                MessageBox.Show(ex.Message);            }            finally            {                db.CloseConnection();            }        }        public string caption = "输入提示";        public void search()        {            if (listView1.Items.Count > 0)            {                listView1.Items.Clear();            }            StringBuilder sb = new StringBuilder();            sb.AppendLine("SELECT  [Name],[Type],[Number],[Price] FROM [Godds]");            sb.AppendFormat("  WHERE  [Type] LIKE '{0}'", this.comboBox1.Text);            SqlCommand comm = new SqlCommand(sb.ToString(), db.Connection);            db.OpenConnection();            SqlDataReader reader = comm.ExecuteReader();            try            {                if (!reader.HasRows)                {                    MessageBox.Show("没有要查找的记录!", caption, MessageBoxButtons.OK, MessageBoxIcon.Information);                }                else                {                    while (reader.Read())                    {                        string Type = reader["Type"].ToString();                        string Name = reader["Name"].ToString();                        int number = Convert.ToInt32(reader["Number"]);                        int price = Convert.ToInt32(reader["Price"]);                        ListViewItem item = new ListViewItem(Name);                        item.SubItems.AddRange(new string[] { Type, number.ToString(), price.ToString() });                        this.listView1.Items.Add(item);                    }                    reader.Close();                }            }            catch (Exception ex)            {                MessageBox.Show(ex.Message);            }            finally            {                db.CloseConnection();            }        }        private void button1_Click(object sender, EventArgs e)        {            search();        }    }}
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