1 private void btnLogin_Click(object sender, EventArgs e)
2 {
3 string txtUserName = this.txtUserName.Text.Trim();
4 string txtPwd = this.txtPwd.Text.Trim();
5 if (txtUserName==null||txtPwd==null||txtUserName.Length==0||txtPwd.Length==0)
6 {
7 MessageBox.Show("您输入的内容为空，请重新输入！");
8 }
9 string connString = "server=.;database=StudentMISDB;uid=sa;pwd=123456";
10 SqlConnection conn = new SqlConnection(connString);
11 conn.Open();
12 string sql = @"select l.*,DATEDIFF(MI,LoginErrorLastTime,GETDATE()) as 间隔 from login as l where loginname=‘{0}‘";
13 sql = string.Format(sql, txtUserName);
14 SqlCommand cmd = new SqlCommand(sql,conn);
15 SqlDataAdapter adapter = new SqlDataAdapter(cmd);
16 DataSet dSet = new DataSet();
17 adapter.Fill(dSet);
18 conn.Close();
19 if (dSet.Tables[0].Rows.Count > 0)
20 {
21 int errorCount = Convert.ToInt32(dSet.Tables[0].Rows[0][3]);
22 int times = Convert.ToInt32(dSet.Tables[0].Rows[0][5]);
23 if (errorCount >= 3 && times <= 15)
24 {
25 if (dSet.Tables[0].Rows[0][1].ToString() == txtUserName && dSet.Tables[0].Rows[0][2].ToString()==txtPwd)
26 {
27 MessageBox.Show("登陆成功");
28 conn.Open();
29 string uptateSql = @"update login set loginerrorcount=0 where id=‘{0}‘";
30 uptateSql = string.Format(uptateSql,dSet.Tables[0].Rows[0][0].ToString());
31 cmd = new SqlCommand(uptateSql,conn);
32 cmd.ExecuteNonQuery();
33 conn.Close();
34 }
35 else
36 {
37 MessageBox.Show("登录名或者密码错误！");
38 conn.Open();
39 string updateSql = @"update login set loginerrorcount=loginerrorcount+1 ,loginerrorlasttime=getdate() where id=‘{0}‘";
40 updateSql = string.Format(updateSql,dSet.Tables[0].Rows[0][0].ToString());
41 cmd = new SqlCommand(updateSql,conn);
42 cmd.ExecuteNonQuery();
43 conn.Close();
44 }
45 }
46 else
47 {
48 MessageBox.Show("请在"+(15-times)+"分钟后登录！");
49 }
50 }
51 else
52 {
53 MessageBox.Show("用户不存在！");
54 }
55 }
56 }
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 ADO.NET8._30
13 {
14 public partial class DataGridView : Form
15 {
16 public DataGridView()
17 {
18 InitializeComponent();
19 }
20
21 private void DataGridView_Load(object sender, EventArgs e)
22 {
23 //加载学生选课信息
24 loadStudntData();
25 //加载课程信息（没有选的课程）
26 LoadCourse();
27 }
28 /// <summary>
29 /// 自定义一个方法
30 /// </summary>
31 private void LoadCourse()
32 {
33 //1.创建数据库连接符
34 string connString = "server=.;database=StudentMISDB;uid=sa;pwd=123456";
35 //2.链接数据库
36 SqlConnection conn = new SqlConnection(connString);
37 //3.添加数据库要执行的语句，通过ID查找没有选择到的课程
38 string sql = @"select * from Course where CourseId not in(select distinct sc.CourseId from [dbo].[Students] as s
39 join Score as sc on s.StudentId=sc.StudentId
40 join Course as c on sc.CourseId = c.CourseId
41 where s.StudentId=‘2‘)";
42 //4.创建命令
43 SqlCommand cmd = new SqlCommand(sql, conn);
44 //5.断开式连接查询
45 SqlDataAdapter da = new SqlDataAdapter(cmd);
46 //6.创建数据缓冲区（数据集）
47 DataSet ds = new DataSet();
48 conn.Open();
49 //7.填充数据集
50 da.Fill(ds);
51 conn.Close();
52 //8.绑定数据源
53 this.cmbCourseName.DataSource = ds.Tables[0];
54
55 //9.设置combobox控件中要显示的列
56 //this.cmboxCourse.DisplayMember = "列名";
57 this.cmbCourseName.DisplayMember = "Name";
58 //10.DisplayMember绑定需要显示的数据表字段，而ValueMember绑定需要获取选择的项的值；直接可见的是此item的 DisplayMember 对应内容，而此 item的值是ValueMember 的对应内容。
59 this.cmbCourseName.ValueMember = "CourseId";
60 }
61 /// <summary>
62 /// 获取选中的值
63 /// </summary>
64 /// <param name="sender"></param>
65 /// <param name="e"></param>
66 private void cmbCourseName_SelectedIndexChanged(object sender, EventArgs e)
67 {
68 string courseID = this.cmbCourseName.SelectedValue.ToString();
69 ///string courseName = this.cmboxCourse.SelectedText;
70 }
71 /// <summary>
72 /// 保存 选课后，
73 /// </summary>
74 /// <param name="sender"></param>
75 /// <param name="e"></param>
76 private void btnSave_Click(object sender, EventArgs e)
77 {
78 //获取到在combobox控件中已经选择的值
79 string courseID = this.cmbCourseName.SelectedValue.ToString();
80 //string courseName = this.cmboxCourse.SelectedText;
81 int studentId = 2;
82 //1.
83 string connString = "server=.;database=StudentMISDB;uid=sa;pwd=123456";
84 SqlConnection conn = new SqlConnection(connString);
85
86 string sql = "insert into Score values(‘{0}‘,‘{1}‘,‘{2}‘)";
87 sql = string.Format(sql, studentId, courseID, 0);
88
89 SqlCommand cmd = new SqlCommand(sql, conn);
90 conn.Open();
91 int result = cmd.ExecuteNonQuery();
92 conn.Close();
93 if (result > 0)
94 {
95 MessageBox.Show("保存成功");
96
97 loadStudntData();
98 LoadCourse();
99 }
100 else
101 {
102 MessageBox.Show("保存失败");
103 }
104 }
105 /// <summary>
106 /// 加载学生选课信息
107 /// </summary>
108 private void loadStudntData()
109 {
110 string connString = "server=.;database=StudentMISDB;uid=sa;pwd=123456";
111 SqlConnection conn = new SqlConnection(connString);
112
113 string sql = @"select s.Studentid,c.courseId, s.Name as 姓名,c.Name as 课程名, sc.Score as 成绩 from [dbo].[Students] as s
114 join Score as sc on s.StudentId=sc.StudentId
115 join Course as c on sc.CourseId = c.CourseId
116 where s.StudentId=‘{0}‘";
117 sql = string.Format(sql, 2);
118
119 SqlCommand cmd = new SqlCommand(sql, conn);
120 SqlDataAdapter da = new SqlDataAdapter(cmd);
121 DataSet ds = new DataSet();
122 conn.Open();
123 da.Fill(ds);
124 conn.Close();
125
126 this.dataGridView1.DataSource = ds;
127 this.dataGridView1.DataMember = ds.Tables[0].TableName;
128 }
129 }
130 }
二、（1）封装的类：
1 using System;
2 using System.Collections.Generic;
3 using System.Data.SqlClient;
4 using System.Linq;
5 using System.Text;
6 using System.Threading.Tasks;
7 using System.Data;
8
9 namespace Demo2
10 {
11 public static class SqlCommon
12 {
13
14 /// <summary>
15 /// 连接字符串
16 /// </summary>
17 public static string connString = "server=.;database=StudentMISDB;uid=sa;pwd=123456";
18
19 /// <summary>
20 /// 执行增删改操作
21 /// </summary>
22 /// <param name="sql">sql语句 参数传入</param>
23 /// <returns></returns>
24 public static int ExecuteSql(string sql)
25 {
26 int result = 0;
27 //创建连接对象new SqlConnection( 连接字符串)
28 SqlConnection conn = new SqlConnection(connString);
29 //创建命令对象 new SqlCommand(sql语句, conn)
30 SqlCommand cmd = new SqlCommand(sql, conn);
31 // 打开数据连接
32 conn.Open();
33 // 执行 sql 命令，返回受影响的行数
34 result = cmd.ExecuteNonQuery();
35 // 关闭数据连接
36 conn.Close();
37 // 把执行结果【受影响的行数】，返回给调用者
38 return result;
39 }
40
41
42 public static DataSet ExecuteQuery(string sql) {
43
44 SqlConnection conn = new SqlConnection(connString);
45 SqlCommand cmd = new SqlCommand(sql, conn);
46 SqlDataAdapter da = new SqlDataAdapter(cmd);
47 DataSet ds = new DataSet();
48 conn.Open();
49 da.Fill(ds);
50 conn.Close();
51
52 return ds;
53 }
54 }
55 }
（二）、调用类
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
11 using System.Data.SqlClient;
12
13 namespace Demo2
14 {
15 public partial class Form1 : Form
16 {
17 public Form1()
18 {
19 InitializeComponent();
20 }
21
22 private void btnAdd_Click(object sender, EventArgs e)
23 {
24 /// 定义变量接收 用户输入的值
25 string loginName = this.txtLoginName.Text.Trim();
26 string pwd = this.txtPWD.Text.Trim();
27
28 ///判断用户是否有输入值
29 if (loginName == "" || loginName == null)
30 {
31 MessageBox.Show("请输入用户名");
32 return;
33 }
34 //string.IsNullOrEmpty(字符串) ==>判断字符串是否为“空字符”或为 null
35 if (string.IsNullOrEmpty(pwd))
36 {
37 MessageBox.Show("请输入密码");
38 return;
39 }
40
41
42 if (isExistsLoginName(loginName))
43 {
44 MessageBox.Show("该用户名已经存在，请重新输入");
45 this.txtLoginName.Text = string.Empty;
46 this.txtPWD.Text = string.Empty;
47 return;
48 }
49
50 string sql = @"insert into LoginInfo (loginName,pwd,LoginErrorLastTime)
51 values(‘{0}‘,‘{1}‘,‘{2}‘)";
52 sql = string.Format(sql, loginName, pwd, DateTime.Now.ToString());
53
54 int row = SqlCommon.ExecuteSql(sql);
55 if (row > 0)
56 {
57 MessageBox.Show("添加成功");
58 }
59 else
60 {
61 MessageBox.Show("添加失败");
62 }
63
64 }
65
66
67 #region 判断 用户名是否存在
68
69 private bool isExistsLoginName(string loginName)
70 {
71 string sql = @"select * from LoginInfo where LoginName=‘{0}‘";
72 sql = string.Format(sql, loginName);
73 DataSet ds = SqlCommon.ExecuteQuery(sql);
74 return ds.Tables[0].Rows.Count > 0;
75 }
76 #endregion
77 }
78 }
（三）、datagrideview插件
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
11 namespace Demo2
12 {
13 public partial class FrmScore : Form
14 {
15 public FrmScore()
16 {
17 InitializeComponent();
18 }
19
20 private void btnSelect_Click(object sender, EventArgs e)
21 {
22 string name = this.txtCourse.Text.Trim();
23
24 string sql = @"select ScoreId,Name,Score from Course as c
25 join Score as sc on c.CourseId = sc.CourseId
26 where sc.StudentId=‘1‘ and c.Name like ‘%{0}%‘";
27 sql = string.Format(sql,name);
28 DataSet ds = SqlCommon.ExecuteQuery(sql);
29
30 this.dataGridView1.DataSource = ds.Tables[0];
31
32 }
33 }
34 }
时间： 2024-12-09 17:43:04