winform连接MySQL数据库帮助类

以下是一个简单的 Winform 连接 MySQL 数据库的帮助类示例。需要先引用 `MySql.Data` 和 `MySql.Data.Types` 两个库。

using MySql.Data.MySqlClient;

public class MySQLHelper
{
    private MySqlConnection connection;
    private string server;
    private string database;
    private string uid;
    private string password;

    // 构造函数
    public MySQLHelper()
    {
        Initialize();
    }

    // 初始化连接字符串
    private void Initialize()
    {
        server = "localhost";
        database = "mydatabase";
        uid = "username";
        password = "password";
        string connectionString;
        connectionString = "SERVER=" + server + ";" + "DATABASE=" +
        database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";";

        connection = new MySqlConnection(connectionString);
    }

    // 打开连接
    private bool OpenConnection()
    {
        try
        {
            connection.Open();
            return true;
        }
        catch (MySqlException ex)
        {
            // 处理异常
            return false;
        }
    }

    // 关闭连接
    private bool CloseConnection()
    {
        try
        {
            connection.Close();
            return true;
        }
        catch (MySqlException ex)
        {
            // 处理异常
            return false;
        }
    }

    // 执行 SQL 命令，返回影响的行数
    public int ExecuteNonQuery(string query)
    {
        if (this.OpenConnection() == true)
        {
            MySqlCommand cmd = new MySqlCommand(query, connection);
            int rowsAffected = cmd.ExecuteNonQuery();
            this.CloseConnection();
            return rowsAffected;
        }
        else
        {
            return -1;
        }
    }

    // 执行 SQL 查询，返回一个 MySqlDataReader 对象
    public MySqlDataReader ExecuteReader(string query)
    {
        if (this.OpenConnection() == true)
        {
            MySqlCommand cmd = new MySqlCommand(query, connection);
            MySqlDataReader dataReader = cmd.ExecuteReader();
            return dataReader;
        }
        else
        {
            return null;
        }
    }

    // 执行 SQL 查询，返回一个 DataTable 对象
    public DataTable ExecuteQuery(string query)
    {
        DataTable dataTable = new DataTable();
        try
        {
            if (this.OpenConnection() == true)
            {
                MySqlCommand cmd = new MySqlCommand(query, connection);
                MySqlDataAdapter adapter = new MySqlDataAdapter(cmd);
                adapter.Fill(dataTable);
            }
        }
        catch (MySqlException ex)
        {
            // 处理异常
        }
        finally
        {
            this.CloseConnection();
        }
        return dataTable;
    }
}

使用方法：

MySQLHelper mysql = new MySQLHelper();
string query = "SELECT * FROM mytable";
DataTable dataTable = mysql.ExecuteQuery(query);
foreach (DataRow row in dataTable.Rows)
{
    Console.WriteLine(row["id"] + " " + row["name"]);
}

其中 `ExecuteNonQuery()` 方法用于执行 INSERT、UPDATE 和 DELETE 命令，返回影响的行数；`ExecuteReader()` 方法用于执行 SELECT 命令，返回一个 MySqlDataReader 对象；`ExecuteQuery()` 方法用于执行 SELECT 命令，返回一个 DataTable 对象。需要根据具体情况选择合适的方法。