数据库增删改查代码，登录和注册

封装字段，定义成员变量

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace data
{
 public class cangkudata
    {
        private string cno;

        public string Cno
        {
            get { return cno; }
            set { cno = value; }
        }
        private string city;

        public string City
        {
            get { return city; }
            set { city = value; }
        }
        private int mianji;

        public int Mianji
        {
            get { return mianji; }
            set { mianji = value; }
        }
    }
}

把增删改查的方法写好，用面向对象思想来调用

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using data;
using System.Data.SqlClient;

namespace DA
{
  public  class cangkuDA
    {
      SqlConnection coon;
      SqlCommand cmd;

      public cangkuDA()
      {
         coon = new SqlConnection("server=.;database=cangku;user=sa;pwd=123");
         cmd = coon.CreateCommand();
      }
      public void Insert(cangkudata data)
      {
          cmd.CommandText = "insert into cangkubiao values(@cno,@city,@mianji)";
          cmd.Parameters.Clear();
          cmd.Parameters.Add("@cno",data.Cno);
          cmd.Parameters.Add("@city",data.City);
          cmd.Parameters.Add("@mianji",data.Mianji.ToString());
          coon.Open();
          cmd.ExecuteNonQuery();
          coon.Close();
      }
      public void Delete(string cno)
      {
          cmd.CommandText = "delete from cangkubiao where cno=@cno";
          cmd.Parameters.Clear();
          cmd.Parameters.Add("@cno",cno);
          coon.Open();
          cmd.ExecuteNonQuery();
          coon.Close();
      }
      public void Update(cangkudata data)
      {
          cmd.CommandText = "update cangkubiao set city=@city,mianji=@mianji where cno=@cno";
          cmd.Parameters.Clear();
          cmd.Parameters.Add("cno",data.Cno);
          cmd.Parameters.Add("city",data.City);
          cmd.Parameters.Add("mianji",data.Mianji);
          coon.Open();
          cmd.ExecuteNonQuery();
          coon.Close();
      }
      public List<cangkudata> Select()
      {
          List<cangkudata> list = new List<cangkudata>();
          cmd.CommandText = "select*from cangkubiao";
          coon.Open();
          SqlDataReader dr = cmd.ExecuteReader();
          if (dr.HasRows )
          {
              while (dr.Read ())
              {
                  cangkudata data = new cangkudata();
                  data.Cno = dr["cno"].ToString();
                  data.City = dr["city"].ToString();
                  data.Mianji =int.Parse ( dr["mianji"].ToString());

                  list.Add(data);
              }
          }
          cmd.Dispose();
          coon.Close();
          return list;
      }
      public List<cangkudata> Select1(string cno,string city,int mianji)
      {
          List<cangkudata> list = new List<cangkudata>();
          cmd.CommandText = "select*from cangkubiao where cno like '%"+cno+"%' and city like '%"+city+"%' and mianji like '%"+mianji+"%'";
          coon.Open();
          SqlDataReader dr = cmd.ExecuteReader();
          if (dr.HasRows)
          {
              while (dr.Read())
              {
                  cangkudata data = new cangkudata();
                  data.Cno = dr["cno"].ToString();
                  data.City = dr["city"].ToString();
                  data.Mianji =int.Parse ( dr["mianji"].ToString());

                  list.Add(data);
              }
          }
          cmd.Dispose();
          coon.Close();
          return list;
      }
      public cangkudata Select2(string cno)
      {
          cangkudata data = null;
          cmd.CommandText = "select*from cangkubiao where cno=@cno";
          cmd.Parameters.Clear();
          cmd.Parameters.Add("@cno",cno);
          coon.Open();
          SqlDataReader dr = cmd.ExecuteReader();
          if (dr.HasRows )
          {
              if (dr.Read ())
              {
                  data = new cangkudata();
                  data.Cno = dr["cno"].ToString();
                  data.City = dr["city"].ToString();
                  data.Mianji =int.Parse ( dr["mianji"].ToString ());
              }
          }
          cmd.Dispose();
          coon.Close();
          return data;
      }
    }
}

写点击事件实现对数据库的增删改查

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using data;
using DA;

namespace 连接仓库
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        //清空
        private void button6_Click(object sender, EventArgs e)
        {
            listView1.Items.Clear();
            comboBox1.Text = null;
            comboBox2.Text = null;
            comboBox3.Text = null;
        }
        //显示界面
        private void Form1_Load(object sender, EventArgs e)
        {
            List<cangkudata> list = new cangkuDA().Select();
            if (list!=null)
            {
                foreach (cangkudata x in list)
                {
                    comboBox1.Items.Add(x.Cno);
                    comboBox2.Items.Add(x.City);
                    comboBox3.Items.Add(x.Mianji);
                }
            }
        }
        //显示方法
        public void  fangfa(List<cangkudata > list)
        {
            listView1.Columns.Clear();
            listView1.Columns.Add("仓库号");
            listView1.Columns.Add("城市");
            listView1.Columns.Add("仓库面积");

            if (listView1.Items !=null)
            {
                listView1.Items.Clear();
                for (int i = 0; i <list.Count; i++)
                {
                      listView1.Items.Add(list[i].Cno);
                      listView1.Items[i].SubItems.Add(list[i].City);
                      listView1.Items[i].SubItems.Add(list[i].Mianji.ToString ());
                }
              
            }
        }
        //查询
        private void button1_Click(object sender, EventArgs e)
        {
            List<cangkudata> list = new cangkuDA().Select();
            fangfa(list);
        }
        //条件查询
        private void button5_Click(object sender, EventArgs e)
        {
            List<cangkudata> list = new cangkuDA().Select1(comboBox1 .Text,comboBox2 .Text ,int.Parse                  (comboBox3 .Text ) );
            fangfa(list);
        }
        //删除
        private void button4_Click(object sender, EventArgs e)
        {
            try
            {
                if (listView1.SelectedItems.Count > 0)
                {
                    string cno = listView1.SelectedItems[0].Text;
                    new cangkuDA().Delete(cno);
                }

                fangfa(new cangkuDA().Select());
            }
            catch
            {
                MessageBox.Show("请先删除外键！");
            }
        }
        //点击修改
        private void button3_Click(object sender, EventArgs e)
        {
            if (listView1 .SelectedItems .Count >0)
            {
                string cno = listView1.SelectedItems[0].Text;
                cangkudata data = new cangkuDA().Select2(cno);
                comboBox1.Text = data.Cno;
                comboBox2.Text = data.City;
                comboBox3.Text = data.Mianji.ToString ();
            }
                cangkudata data1= new cangkudata();
                data1.Cno = comboBox1.Text;
                data1.City = comboBox2.Text;
                data1.Mianji =int.Parse (comboBox3.Text);
                new cangkuDA().Update(data1);
                fangfa(new cangkuDA ().Select());
        }
        //添加
        private void button2_Click(object sender, EventArgs e)
        {
           
                cangkudata data = new cangkudata();
                data.Cno = comboBox1.Text;
                data.City = comboBox2.Text;
                data.Mianji = int.Parse(comboBox3.Text);

                new cangkuDA().Insert(data);
                fangfa(new cangkuDA().Select());
           
        }
    }
}

注册界面的代码，实际就是向数据库添加数据的过程

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using data4;
using DA4;
using 连接仓库.管理员;
using data5;
using DA5;

namespace 连接仓库
{
    public partial class zhucejiemian : Form
    {
        public zhucejiemian()
        {
            InitializeComponent();
        }
        //显示界面
        private void zhucejiemian_Load(object sender, EventArgs e)
        {
            sheng();
           
        }
        private void sheng()
        {
            List<dizhidata> list = new dizhiDA().Select();
            foreach (dizhidata x in list)
            {
                comboBox1.Items.Add(x.Sheng);
                comboBox1.Text = comboBox1.Items[0].ToString();
            }
        }
        private void shi()
        {
            List<dizhidata> list = new dizhiDA().Selectsheng(comboBox1.Text);
            foreach (dizhidata x in list)
            {
                comboBox2.Items.Add(x.Shi);
                comboBox2.Text = comboBox2.Items[0].ToString();
            }
        }
        private void qu()
        {
            List<dizhidata> list = new dizhiDA().Selectshi(comboBox2.Text);
            foreach (dizhidata x in list)
            {
                comboBox3.Items.Add(x.Qu);
                
            }
        }
        //当点击城市的时候
        private void button2_Click(object sender, EventArgs e)
        {
            comboBox2.Items.Clear();
             shi();
            comboBox2.Text = comboBox2.Items[0].ToString ();
        
        }
        //当点击区县的时候
        private void button3_Click(object sender, EventArgs e)
        {
            comboBox3.Items.Clear();
            qu();
            comboBox3.Text = comboBox3.Items[0].ToString();
        }

        //当点击注册的时候
        private void button1_Click(object sender, EventArgs e)
        {
            zhucehoutaidata5 data = new zhucehoutaidata5();
            data.Nicheng = textBox1.Text;
            data.Mima = textBox2.Text;
            data.Mima1 = textBox3.Text;
            data.Xingming = textBox4.Text;
            data.Haoma = textBox5.Text;
            data.Phone = textBox6.Text;
            data.Youxiang = textBox7.Text;
            data.Sheng = comboBox1.Text;
            data.Shi = comboBox2.Text;
            data.Qu = comboBox3.Text;

            new zhucehoutaiDA().Insert(data);

            bool a;
            try
            {
                a = true;
                string x = textBox6.Text;
                for (int i = 0; i < x.Length; i++)
                {
                    string x1 = x.Substring(i, 1);
                    int x2 = Convert.ToInt32(x1);
                }
            }
            catch
            {
                a = false;
            }

            if (textBox1.Text.Length==0)
            {
                MessageBox.Show("昵称不能为空");
            }
            else if (textBox2 .Text.Length==0)
            {
                MessageBox.Show("密码不能为空");
            }
            else if (textBox3.Text!=textBox2.Text )
            {
                MessageBox.Show("两次输入密码不一致");
            }
            else if (textBox4.Text.Length ==0)//怎样判断是否输入的汉字？？
            {

                MessageBox.Show("姓名不能为空");
               
            }
            else if (textBox5.Text.Trim().Length==0)
            {
                MessageBox.Show("请输入您的身份证号码");
            }
            else if (textBox6.Text.Trim().Length == 0 || textBox6.Text.Trim().Length < 11 || a==false)
            {    
                    MessageBox.Show("请输入正确手机号");      
            }  

            else if (!textBox7.Text.Contains("@") && !textBox7.Text.Contains(".com"))
            {
                MessageBox.Show("请输入一个正确的邮箱格式");
            }
            else
            {
                MessageBox.Show("恭喜你注册成功！");
                denglu f = new denglu();
                this.Visible = false;
                this.Owner = f;
                f.Show();
            }
        }
      
    }
}

登陆界面实际就是一个查询过程

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using data1;
using DA1;
using data5;
using DA5;

namespace 连接仓库.管理员
{
    public partial class denglu : Form
    {
        public denglu()
        {
            InitializeComponent();
        }

        private void denglu_Load(object sender, EventArgs e)
        {
            
            List<zhucehoutaidata5> list = new zhucehoutaiDA().Select1();
            if (list!=null)
            {
                foreach (zhucehoutaidata5 x in list)
                {
                    comboBox1.Items.Add(x.Nicheng);    
                }
            }
        }
        //点击登录按钮
        private void button1_Click(object sender, EventArgs e)
        {
            string nicheng=comboBox1.Text;
            string mima=textBox1 .Text ;
            List<zhucehoutaidata5> list = new zhucehoutaiDA().Select(nicheng,mima);
            if (list != null)
            {
                MessageBox.Show("登录成功");
                cangkuguanli f = new cangkuguanli();
                this.Owner = f;
                f.WindowState = FormWindowState.Maximized; //这句话什么意思
                this.Visible = false;
                f.Show();
            }
            else
            {
                MessageBox.Show("登录失败");
            }

            
            /*if (list != null)
            {
                foreach (zhigongdata x in list)
                {
                    comboBox1.Items.Add(x.Cno);
                    comboBox2.Items.Add(x.Zno);
                }
               
            }
            if (comboBox1.Text == comboBox1.Items[0].ToString() && comboBox2.Text == comboBox2.Items[1].ToString())
            {
                MessageBox.Show("登录成功");
                cangkuguanli f = new cangkuguanli();
                this.Owner = f;
                f.WindowState = FormWindowState.Maximized; //这句话什么意思
                this.Visible = false;  
                f.Show();
            }
            else
            {
                MessageBox.Show("登录失败");
            }*/
        }
        //当点击注册的时候
        private void button2_Click(object sender, EventArgs e)
        {
            zhucejiemian f = new zhucejiemian();
    
            this.Visible = false;
            this.Owner = f;
            f.Show();
        }
    }
}