winform是窗体项目
该winform 项目使用的数据库是mysql，vs版本是2022
创建一个net framework项目
随便选一个框架版本
将form窗体中加入 一个DataGridView、四个button（新增、更新、删除、查询）按钮、一个textbox。这些控件在 视图---工具栏
把窗体中的button按钮名字都改掉，方便查看
在项目中创建一个student实体类
/// <summary>
/// 学号
/// </summary>
public int studentId { get; set; }
/// <summary>
/// 姓名
/// </summary>
public string sName { get; set; }
/// <summary>
/// 年龄
/// </summary>
public int sAge { get; set; }
/// <summary>
/// 爱好
/// </summary>
public string sLike { get; set; }
public Student(int studentId, string sName, int sAge, string sLike)
{
this.studentId = studentId;
this.sName = sName;
this.sAge = sAge;
this.sLike = sLike;
}
相对应mysql库中也要建一个student表，现在我们先手动创建数据库表，后期再给大家说EF映射
写语句创建库
CREATE DATABASE StudentCase
创建学生表student
CREATE TABLE student( studentid INT PRIMARY KEY, sname VARCHAR(100) , sage INT , slike VARCHAR(200) )
因为用的是mysql数据库，所以要引用mysql在net framwork 中对应的dll文件：MySql.Data
新增按钮是跳转到另外的表单上面，所以我们再创建一个 StudentManager 窗体 （表单创建4个label、4个textbox、1个button）
删改查代码
public partial class StudentManager : Form
{
public List<Student> students = null;
public StudentManager()
{
InitializeComponent();
}
private string connectionStr = "server=127.0.0.1;port=3306;user=root;password=root;database=studentcase";//连接数据库
private void Form1_Load(object sender, EventArgs e)
{
}
private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
}
/// <summary>
/// 更新
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void edit_Click(object sender, EventArgs e)
{
//dataGridView1.DataSource.students
Student student= students[dataGridView1.CurrentRow.Index];
string editStr = $"update student set studentId={dataGridView1["studentId", dataGridView1.CurrentRow.Index].Value},sName='{dataGridView1["sName", dataGridView1.CurrentRow.Index].Value}',sAge={dataGridView1["sAge", dataGridView1.CurrentRow.Index].Value},sLike='{dataGridView1["sLike",dataGridView1.CurrentRow.Index].Value}' where studentId='{student.studentId}'";
MySqlConnection mySqlConnection = new MySqlConnection(connectionStr);
mySqlConnection.Open();
MySqlCommand mySqlCommand = new MySqlCommand(editStr, mySqlConnection);
mySqlCommand.ExecuteNonQuery();//对连接执行SQL语句并返回行数
mySqlCommand.Dispose();//释放MySqlCommand资源
mySqlConnection.Close();
}
/// <summary>
/// 删除
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void delete_Click(object sender, EventArgs e)
{
Student student = students[dataGridView1.CurrentRow.Index];
string delStr = $"delete from student where studentId={dataGridView1["studentId", dataGridView1.CurrentRow.Index].Value}";
MySqlConnection mySqlConnection = new MySqlConnection(connectionStr);
mySqlConnection.Open();
MySqlCommand mySqlCommand = new MySqlCommand(delStr,mySqlConnection);
mySqlCommand.ExecuteNonQuery();
mySqlCommand.Dispose();
mySqlConnection.Close();
}
/// <summary>
/// 添加
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void button1_Click(object sender, EventArgs e)
{
new AddOrEdit().Show();//指定展示控件
}
/// <summary>
/// 查询
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void query_Click(object sender, EventArgs e)
{
string QueryStr = "select * from student";
MySqlConnection mySqlConnection = new MySqlConnection(connectionStr);
MySqlCommand mySqlCommand = new MySqlCommand(QueryStr, mySqlConnection);
mySqlConnection.Open();
MySqlDataReader mySqlDataReader = mySqlCommand.ExecuteReader();
students = new List<Student>();
while (mySqlDataReader.Read())
{
students.Add(new Student(int.Parse(mySqlDataReader[0].ToString()), mySqlDataReader[1].ToString(), int.Parse(mySqlDataReader[2].ToString()), mySqlDataReader[3].ToString()));
}
mySqlCommand.Dispose();
mySqlConnection.Close();
dataGridView1.DataSource = students;
}
}
添加代码
public partial class AddOrEdit : Form
{
public AddOrEdit()
{
InitializeComponent();
}
private string connectionStr = "server=127.0.0.1;port=3306;user=root;password=root;database=studentcase";//连接数据库
private void textstudentId_TextChanged(object sender, EventArgs e)
{
//var reader = mySqlCommand.ExecuteReader();
}
/// <summary>
/// 添加
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void button1_Click(object sender, EventArgs e)
{
string addStr = $"insert into student(studentId,sName,sAge,sLike) values({int.Parse(textstudentId.Text)},'{textname.Text}',{int.Parse(textage.Text)},'{textlike.Text}');";
MySqlConnection mySqlConnection = new MySqlConnection(connectionStr);
MySqlCommand mySqlCommand = new MySqlCommand(addStr, mySqlConnection);
mySqlConnection.Open();
mySqlCommand.ExecuteNonQuery();
mySqlCommand.Dispose();
mySqlConnection.Close();
textstudentId.Text = "";//清空text内容
textname.Text = "";
textage.Text = "";
textlike.Text = "";
}
}
本节遇到的问题
“张三“ 是四个字节一个单位进行编码的，而我们通常使用的utf-8编码在mysql数据库中默认是按照3个字节一个单位进行编码的，正是这个原因导致将数据存入mysql数据库的时候出现错误
解决方法：输入失sql语句alter table `student` convert to character set utf8mb4
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