C#学习笔记（6）——大项目增删改查

  1 using System;
  2 using System.Collections.Generic;
  3 using System.ComponentModel;
  4 using System.Data;
  5 using System.Drawing;
  6 using System.Linq;
  7 using System.Text;
  8 using System.Threading.Tasks;
  9 using System.Windows.Forms;
 10 using System.Data.SqlClient;
 11 
 12 namespace _03大项目查找
 13 {
 14     public partial class Form1 : Form
 15     {
 16         public Form1()
 17         {
 18             InitializeComponent();
 19 
 20         }
 21         string str = "Data Source=.; Initial Catalog=mysql; Integrated Security=True;";
 22 
 23         private void Form1_Load(object sender, EventArgs e)
 24         {
 25 
 26             loadStudent(0);
 27         }
 28         /// <summary>
 29         /// 加载学生信息
 30         /// </summary>
 31         /// <param name="p">p是删除标识，0删除，1未删除</param>
 32         public void loadStudent(int p)
 33         {
 34             List<Student> list = new List<Student>();
 35 
 36             using (SqlConnection con = new SqlConnection(str))
 37             {
 38                 con.Open();
 39                 string sql = "select id, name, chinese, math, flag from myclass where flag = " + p;
 40                 using (SqlCommand cmd = new SqlCommand(sql, con))
 41                 {
 42                     using (SqlDataReader reader = cmd.ExecuteReader())
 43                     {
 44                         if (reader.HasRows)
 45                         {
 46                             while (reader.Read())
 47                             {
 48                                 Student st = new Student();
 49                                 st.Id = Convert.ToInt32(reader["id"]);
 50                                 st.Name = Convert.ToString(reader["name"]);
 51                                 st.Chinese = Convert.ToString(reader["chinese"]);
 52                                 st.Math = Convert.ToString(reader["math"]);
 53                                 st.Flag = Convert.ToInt32(reader["flag"]);
 54                                 list.Add(st);
 55                             }
 56                         }
 57                     }
 58                 }
 59             }
 60 
 61             dgv.DataSource = list;
 62             dgv.SelectedRows[0].Selected = false;
 63         }
 64         /// <summary>
 65         /// 添加学生信息
 66         /// </summary>
 67         /// <param name="sender"></param>
 68         /// <param name="e"></param>
 69         private void button1_Click(object sender, EventArgs e)
 70         {
 71             int n = -999;
 72             string name = txtName.Text;
 73             string chinese = txtChinese.Text;
 74             string math = txtMath.Text;
 75             string sql = string.Format("insert into myclass(name,chinese,math,flag) values(‘{0}‘,‘{1}‘,‘{2}‘,0)", name, chinese, math);
 76             using (SqlConnection con = new SqlConnection(str))
 77             {
 78                 using (SqlCommand cmd = new SqlCommand(sql, con))
 79                 {
 80                     con.Open();
 81                     n = cmd.ExecuteNonQuery();
 82                     MessageBox.Show(n > 0 ? "操作成功！" : "操作失败！");
 83                 }
 84             }
 85             loadStudent(0);
 86 
 87             //MessageBox.Show("123");
 88         }
 89         /// <summary>
 90         /// 删除学生
 91         /// </summary>
 92         /// <param name="sender"></param>
 93         /// <param name="e"></param>
 94         private void btnDel_Click(object sender, EventArgs e)
 95         {
 96             int n = -999;
 97             string id = dgv.SelectedRows[0].Cells[0].Value.ToString();
 98             string name = dgv.SelectedRows[0].Cells[1].ToString();
 99             string chinese = dgv.SelectedRows[0].Cells[2].ToString();
100 
101             string sql = string.Format("update myclass set flag = 1 where id ={0}", id);
102             using (SqlConnection con = new SqlConnection(str))
103             {
104                 using (SqlCommand cmd = new SqlCommand(sql, con))
105                 {
106                     con.Open();
107                     n = cmd.ExecuteNonQuery();
108                     MessageBox.Show(n > 0 ? "操作成功！" : "操作失败！s");
109                 }
110             }
111             loadStudent(0);
112         }
113         /// <summary>
114         /// 选中一行，显示在修改框中
115         /// </summary>
116         /// <param name="sender"></param>
117         /// <param name="e"></param>
118         private void dgv_CellClick(object sender, DataGridViewCellEventArgs e)
119         {
120             lbId.Text = dgv.SelectedRows[0].Cells[0].Value.ToString();
121             txtUname.Text = dgv.SelectedRows[0].Cells[1].Value.ToString();
122             txtUchinese.Text = dgv.SelectedRows[0].Cells[2].Value.ToString();
123             txtUmath.Text = dgv.SelectedRows[0].Cells[3].Value.ToString();
124             
125         }
126 
127         private void btnUpdate_Click(object sender, EventArgs e)
128         {
129             int n = -999;
130             if (dgv.SelectedRows.Count>0)
131             {
132                 string sql = string.Format("update myclass set name = {0}, chinese = {1}, math = {2} where id = {3}", txtUname.Text,txtUchinese.Text,txtUmath.Text,lbId.Text);
133                 using (SqlConnection con = new SqlConnection(str))
134                 {
135                     using (SqlCommand cmd = new SqlCommand(sql,con))
136                     {
137                         con.Open();
138                         n = cmd.ExecuteNonQuery();
139                         MessageBox.Show(n>0?"操作成功！":"操作失败！");
140                     }
141                 }
142             }
143             else
144             {
145                 MessageBox.Show("请输入数据！");
146             }
147             loadStudent(0);
148         }
149     }
150 }