Question

我希望在用户关闭表单之前将Windows窗体应用程序与服务器断开连接。因此，我使用FormClosing事件;

FormClosing += FormManager_FormClosing;

我尝试使用Backgroundworker或没有Backgroundworker，但它无法正常工作。

我编写的代码;

public partial class MqttManager : Form
    {
        MqttHandler mqttHandler = new MqttHandler();
        ...
        public MqttManager()
        {
            InitializeComponent();
            ...
            // Specify what will happen while form is closing.
            FormClosing += MqttManager_FormClosing;
        }
        /// <summary>
        /// Disconnect from the broker while form is closing.
        /// </summary>
        private void MqttManager_FormClosing(object sender, FormClosingEventArgs e)
        {
            bool isDisconnected = mqttHandler.Disconnect();
            while (!isDisconnected)
            {
                System.Threading.Thread.Sleep(1000);
            }

            //disconnBgWorker.RunWorkerAsync();
        }

        private void disconnBgWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            statusPctBox.WaitOnLoad = false;
            statusPctBox.Image = Properties.Resources.bigCircle;
            System.Threading.Thread.Sleep(1000);
        }

        private void disconnBgWorker_RunWorkerCompleted(
            object sender,
            RunWorkerCompletedEventArgs e)
        {
            bool isDisconnected = mqttHandler.Disconnect();
            if (isDisconnected)
            {
                statusPctBox.Image = Properties.Resources.x32;
                flag = true;
            }
            else
                statusPctBox.Image = Properties.Resources.ok32;
        }
    }

class MqttHandler
    {
        ...
        public MqttHandler() { }
        ...

        /// <summary>
        /// Disconnect from the broker.
        /// </summary>
        public bool Disconnect()
        {
            try
            {
                client.Disconnect();
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }
    }

编辑：“使用while（！isDisconnected）”时，我得到“System.Windows.Forms.dll中发生了'System.ObjectDisposedException'类型的未处理异常附加信息：无法访问已处置的对象。“表单关闭后的消息。

解决方案：首先，谢谢你们所有人。我在代码上发现了自己的错误。断开连接后，触发了一个事件处理程序并尝试使用“Invoke”更改UI元素。那一刻发生了错误。为了解决这个问题，我断开连接后从相关对象中删除了相关的事件处理程序。

如何在窗体关闭之前运行方法？

0 个答案: