商品打折管理信息系统 使用C#开发，使用软件是visual studio 2017

页面做的比较简单。
下图左边程序主界面，右边是各个页面的代码。

主程序入口代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace sale
{
    static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
           Application.Run(new Login());
           // Application.Run(new MainForm());//测试用
        }
    }
}

下面是主页面代码。

using System;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;

namespace sale
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
          InitializeComponent();
        }

        private void button3_Click(object sender, EventArgs e)//修改
        {
           Change form = new Change();
            form.Show();
        }

        private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)//添加
        {
            Add form = new Add();//新建一个对象，打开添加窗口
            form.Show();
        }

        private void button4_Click(object sender, EventArgs e)//删除 不会写直接删除，只好和其他一样，多做一个窗口
        {
            Delete form = new Delete();//打开删除的页面
            form.Show();
        }

        private void button5_Click(object sender, EventArgs e)//查询
        {

               if (this.textBox1.Text.Trim() == "")
            {
                MessageBox.Show("请输入要查询的商品名称", "提示");
            }
                else{
                string str = @"Data Source=zky\sqlexpress;Initial Catalog=sale;Integrated Security=True";
                SqlConnection conn = new SqlConnection(str);
                conn.Open();
                SqlCommand cmd = new SqlCommand();//绑定SqlConnection对象
                cmd.CommandText = "Select* from good where name_good='" + this.textBox1.Text.Trim() + "'";//
                cmd.Connection = conn;
                SqlDataAdapter sda = new SqlDataAdapter(cmd);
                DataSet ds = new DataSet();//数据集
                sda.Fill(ds);
                this.dataGridView1.DataSource = ds;
                this.dataGridView1.DataMember = ds.Tables[0].ToString();//依次赋值
                this.dataGridView1.AutoGenerateColumns =true;
                dataGridView1.ReadOnly = true;//不允许直接在列表上编辑
                dataGridView1.Columns[2].Visible = false;//第2列不出现在表中
                dataGridView1.Columns[4].Visible = false;//第4列不出现在表中
                dataGridView1.Columns[5].Visible = false;//第5列不出现在表中
                conn.Close();    
            }

        }

        private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)//主显示框
        {

        }

        private void dataGridView2_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {

        }

        private void MainForm_Load(object sender, EventArgs e)
        {
            // TODO: 这行代码将数据加载到表“saleDataSet.good”中。您可以根据需要移动或删除它。
            this.goodTableAdapter.Fill(this.saleDataSet.good);

        }

        private void button6_Click(object sender, EventArgs e)//显示所有商品的信息
        {
            string str = @"Data Source=zky\sqlexpress;Initial Catalog=sale;Integrated Security=True";
            SqlConnection conn = new SqlConnection(str);
            conn.Open();

            SqlDataAdapter sqlDap = new SqlDataAdapter("Select Id_good,name_good,price,sale from good", conn);
            DataSet dds = new DataSet();//数据集
            sqlDap.Fill(dds);
           DataTable _table = dds.Tables[0];
            int count = _table.Rows.Count;
            dataGridView1.DataSource = _table;
            this.dataGridView1.AutoGenerateColumns = true;
            conn.Close();
            conn.Close();
        }

        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void label2_Click(object sender, EventArgs e)
        {

        }

        private void textBox1_TextChanged(object sender, EventArgs e)//商品名称
        {

        }
    }
}

然后是登陆窗口

代码：

using System;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;
using System.Drawing;

namespace sale
{
    public partial class Login : Form
    {
        public Login()
        {
            InitializeComponent();
        }
        public new FormStartPosition StartPosition { get; set; }
        private void button1_Click(object sender, EventArgs e)//注册
        {
            this.Hide();
            Register f5 = new Register();
            f5.ShowDialog();
        }//打开注册页面

        private void label2_Click(object sender, EventArgs e)
        {

        }
        private void button2_Click(object sender, EventArgs e)//登陆
        {
            //数据库连接字符串（引号中的字符串为之前复制的那段字符）  
            //Data source=服务器名，Initial catalog=数据库名，User Id=sqlserver连接名，  
            //Password=数据库连接密码,integrated Security=True  
            string str = @"Data Source=zky\sqlexpress;Initial Catalog=sale;Integrated Security=True";
            SqlConnection conn = new SqlConnection(str);
            conn.Open();
            string selectsql = "Select * from login where username = '" + textBox1.Text + "' and password='" + textBox2.Text + "'";
            SqlCommand cmd = new SqlCommand(selectsql, conn); //SqlCommand对象允许你指定在数据库上执行的操作的类型。  
            cmd.CommandType = CommandType.Text;//这就是告诉cmd执行的sql是你赋给CommandText的值里写出的sql语句，如果是存储过程的话cmd.CommandType = CommandType.StoredProcedure;
            //然后CommandText='存储过程的名字'，这就是告诉cmd执行的是存储过程，  
            //存储过程的名字就是CommandText的值  
            SqlDataReader sdr;
            sdr = cmd.ExecuteReader();
            if (sdr.Read())//显示登录界面；
            {
                MessageBox.Show("登陆成功", "提示");
                MainForm  form= new MainForm();//登陆成功显示主界面  
               // MainForm.StartPosition = FormStartPosition.CenterScreen;

                form.Show();
            }
            else
            {
                MessageBox.Show("登陆失败!请检查用户名或者密码重新登陆！", "提示");//弹出窗口提示用户                                   
                return;
            }
            conn.Close();
        }

        private void Form4_Load(object sender, EventArgs e)
        {

        }

        private void label3_Click_1(object sender, EventArgs e)
        {

        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {

        }
    }
}

注册：

代码：

using System;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;

namespace sale
{
    public partial class Register : Form
    {
        public Register()
        {
            InitializeComponent();
        }
        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void label2_Click(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            string str = @"Data Source=zky\sqlexpress;Initial Catalog=sale;Integrated Security=True";
            SqlConnection conn = new SqlConnection(str);
            conn.Open();
            string selectsql = "select username from login";//验证用户名是否重复          
            SqlCommand com = new SqlCommand(selectsql, conn);
            SqlDataReader reader;
            reader = com.ExecuteReader();
            while(reader.Read())
            if (textBox1.Text == reader["username"].ToString().Trim())
            {
                MessageBox.Show("用户名已经存在，请重新输入！", "提示");//弹出窗口提示用户
                return;
            }
            else if (textBox1.Text != reader["username"].ToString().Trim())//注册成功显示登陆页面 
            {
                conn.Close();
                conn.Open();
                string insertsql = "insert into login values('" + textBox1.Text + "','" + textBox2.Text + "') ";
                SqlCommand cmd = new SqlCommand(insertsql, conn);// 定义cmd对象并连接数据库
                cmd.CommandType = CommandType.Text;//存储过程
                cmd.ExecuteNonQuery();
                MessageBox.Show("恭喜您，注册成功！", "提示");
                this.Close();//关闭注册窗口
                Login form = new Login(); //打开登陆窗口
                form.Show();
                return;
             }
            conn.Close();// 关闭对象并释放所占内存空间
            conn.Dispose();
        }

        private void Form5_Load(object sender, EventArgs e)
        {

        }
    }
}

添加页面：

代码：

using System;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;

namespace sale
{
    public partial class Add : Form
    {
        public Add()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string code;
            code = Convert.ToString(this.textBox1.Text);
            System.Text.RegularExpressions.Regex regex = new System.Text.RegularExpressions.Regex(@"'", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
            code = regex.Replace(code, " ");
            string str = @"Data Source=zky\sqlexpress;Initial Catalog=sale;Integrated Security=True";
            SqlConnection conn = new SqlConnection(str);
            conn.Open();
            string sql = "select count(*) from good where Id_good=('" + code + "')";
            SqlCommand cmd1 = new SqlCommand(sql, conn);
            int count = (int)cmd1.ExecuteScalar();
            if (count > 1)
                MessageBox.Show("商品已经！", "提示");
            else
            {
                SqlCommand cmd = conn.CreateCommand();//值得注意
                cmd.CommandText = "insert into good(Id_good,name_good,sale,price,Id_supplier,Id_shelf,Id_kind) values (@Id_good,@sale,@name_good,@price,@Id_supplier,@Id_shelf,@Id_kind)";//注意逗号用英文的
                cmd.Parameters.Add("@Id_good", SqlDbType.NVarChar);//
                cmd.Parameters.Add("@sale", SqlDbType.VarChar, 20);
                cmd.Parameters.Add("@price", SqlDbType.VarChar, 50);
                cmd.Parameters.Add("@name_good", SqlDbType.VarChar, 20);
                cmd.Parameters.Add("@Id_supplier", SqlDbType.NVarChar);
                cmd.Parameters.Add("@Id_kind", SqlDbType.NVarChar);
                cmd.Parameters.Add("@Id_shelf", SqlDbType.NVarChar);

                cmd.Parameters["@Id_good"].Value = textBox1.Text.Trim();
                cmd.Parameters["@sale"].Value = textBox2.Text.Trim();
                cmd.Parameters["@price"].Value = textBox3.Text.Trim();
                cmd.Parameters["@name_good"].Value = textBox4.Text.Trim();
                cmd.Parameters["@Id_supplier"].Value = textBox5.Text.Trim();
                cmd.Parameters["@Id_kind"].Value = textBox6.Text.Trim();
                cmd.Parameters["@Id_shelf"].Value = textBox7.Text.Trim();
                try
                {
                    conn.Open();
                    if (cmd.ExecuteNonQuery() == 1)
                        MessageBox.Show("商品写入成功！", "提示");
                }
                catch
                {
                    MessageBox.Show("商品已存在，写入失败！", "提示");
                    this.Close();
                }
                //cmd.ExecuteNonQuery();//增加了一条新纪录，所以返回1
                                      /*if (cmd.ExecuteNonQuery() > 0)
                                         MessageBox.Show( "数据写入成功！", "提示");
                                     else
                                         MessageBox.Show("数据写入错误！", "提示");
                                         */

                conn.Close();
                this.Close();
            }

        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox3_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox4_TextChanged(object sender, EventArgs e)
        {

        }

        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void textBox5_TextChanged(object sender, EventArgs e)//供货商
        {

        }

        private void textBox7_TextChanged(object sender, EventArgs e)//货架
        {

        }

        private void textBox6_TextChanged(object sender, EventArgs e)//kind 类型
        {

        }

        private void label5_Click(object sender, EventArgs e)
        {

        }
    }
}

删除：

代码：

using System;
using System.Data.SqlClient;
using System.Windows.Forms;
using System.Data;

namespace sale
{
    public partial class Delete : Form
    {
        public Delete()
        {
            InitializeComponent();
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string str = @"Data Source=zky\sqlexpress;Initial Catalog=sale;Integrated Security=True";
            SqlConnection conn = new SqlConnection(str);
            conn.Open();
            SqlCommand cmd = new SqlCommand("delete from good where Id_good='" + this.textBox1.Text.Trim() + "'");
            cmd.Connection = conn;
            cmd.Parameters.Add("@Id_good", SqlDbType.NVarChar);
            cmd.Parameters["@Id_good"].Value = textBox1.Text.Trim();
            cmd.ExecuteNonQuery();
            conn.Close();
            this.Close();
        }

        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void Delete_Load(object sender, EventArgs e)
        {

        }
    }
}

修改：

代码：

using System;
using System.Data;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace sale
{
    public partial class Change : Form
    {
        public Change()
        {
            InitializeComponent();
        }

        private void Form3_Load(object sender, EventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {

             if (textBox2.Text.Trim() == "" || textBox3.Text.Trim() == "" )
            {
                MessageBox.Show("请输入完整信息！", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else
            {

            string str = @"Data Source=zky\sqlexpress;Initial Catalog=sale;Integrated Security=True";
            SqlConnection conn = new SqlConnection(str);
            conn.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = "update good set  [e-mail]  where [e-mail]_good";
            cmd.Connection = conn;
            cmd.Parameters.Add("@Id_good", SqlDbType.NVarChar);
            cmd.Parameters.Add("@sale", SqlDbType.VarChar, 50);
            cmd.Parameters["@Id_good"].Value = textBox2.Text.Trim();
            cmd.Parameters["@sale"].Value = textBox3.Text.Trim();
            cmd.ExecuteNonQuery();
            conn.Close();
            this.Close();
            }

        }

        private void textBox3_TextChanged(object sender, EventArgs e)
        {

        }
    }
}