net framwork winform

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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