在最大化之前触发密码提示的最大化按钮?

WindowsForms上没有OnMaximize事件。幸运的是,您可以操纵WndProc事件来捕获与单击最大化按钮相对应的系统消息。

尝试将此代码放在表单的代码后面:

编辑: 更新以在标题栏中双击(由Reza Aghaei回答建议)。

protected override void WndProc(ref Message m)
{
    // 0x112: A click on one of the window buttons.
    // 0xF030: The button is the maximize button.
    // 0x00A3: The user double-clicked the title bar.
    if ((m.Msg == 0x0112 && m.WParam == new IntPtr(0xF030)) || (m.Msg == 0x00A3 && this.WindowState != FormWindowState.Maximized))
    {
        // Change this code to manipulate your password check.
        // If the authentication fails, return: it will cancel the Maximize operation.
        if (MessageBox.Show("Maximize?", "Alert", MessageBoxButtons.YesNo) == DialogResult.No)
        {
            // You can do stuff to tell the user about the failed authentication before returning
            return;
        }
    }

    // If any other operation is made, or the authentication succeeds, let it complete normally.
    base.WndProc(ref m);
}

为了完成Ismael的好答案,如果你使用这种方式,我应该提到,这种方式用户可以通过双击标题栏来最大化,所以你应该将这个案例添加到Ismael代码中:

case 0x00A3:
    // Change this code to manipulate your password check.
    // If the authentication fails, return: it will cancel the Maximize operation.
    if (MessageBox.Show("Maximize?", "Alert", MessageBoxButtons.YesNo) == DialogResult.No)
    {
        // You can do stuff to tell the user about the failed authentication before returning
        return;
    }
    break;