C# 事件（event）入門：讓 InitDb 完成時「主動通知」你，而不是回頭猜

public static event EventHandler<(bool IsSuccess, string Message)>? OnDbInitResult;

using Microsoft.Data.Sqlite;

public static class DbHelper
{
    public static event EventHandler<(bool IsSuccess, string Message)>? OnDbInitResult;

    public static void InitDb(string connStr)
    {
        try
        {
            using (var conn = new SqliteConnection(connStr))
            {
                conn.Open();
                string sql = """
                    CREATE TABLE IF NOT EXISTS Products (
                        Id       INTEGER PRIMARY KEY AUTOINCREMENT,
                        Name     TEXT,
                        Category TEXT,
                        Quantity INTEGER,
                        Price    REAL
                    );
                    """;
                using (var cmd = new SqliteCommand(sql, conn))
                {
                    cmd.ExecuteNonQuery();
                    OnDbInitResult?.Invoke(null, (true, "資料庫開啟成功!"));
                }
            }
        }
        catch (Exception ex)
        {
            OnDbInitResult?.Invoke(null, (false, $"資料庫初始化失敗：{ex.Message}"));
        }
    }
}

public MainForm()
{
    InitializeComponent();

    // ...其他初始化...

    // 先訂閱，再呼叫 InitDb
    MySqlDbHelper.OnDbInitResult += MySqlDbHelper_OnDbInitResult;

    MySqlDbHelper.InitDb();
    DbHelper.InitDb();
    all = DbHelper.GetAllProducts();

    RefreshView();
}

private void MySqlDbHelper_OnDbInitResult(object? sender, (bool IsSuccess, string Message) e)
{
    MessageBox.Show(e.Message);
}

private static string connStr =
    "Server=gateway01.xxxx.prod.aws.tidbcloud.com;" +
    "Database=MyInventory;" +
    "Uid=xxxxxxxx.root;" +
    "Pwd=你的密碼;" +          // ← 就是這一行
    "Port=4000;" +
    "SslMode=Preferred;";

// MVP 篇：View 引發、Presenter 訂閱
public event EventHandler AddClicked;
// ...
_view.AddClicked += OnAddClicked;