后台工作者自定义取消消息

Question

如何在后台工作人员的取消事件中显示自定义取消消息

我在 DoWork 事件中使用以下代码取消工作人员

string custom_cancel_msg="Cancelling BG WORKER due to some xxx reeasons";
if (bw.WorkerSupportsCancellation == true)
{
      bw.CancelAsync();
}

如何在完成的事件中显示它。我只能访问以下内容

 if ((e.Cancelled == true))
        {
            lblMessage.Text = "Transaction Canceled in between!"; 
           //HOW CA|N I ACCESS THE CUSTOM MESSA|GE HERE??????????????????
        }

        else if (!(e.Error == null))
        {
            lblMessage.Text = ("Error: " + e.Error.Message);
        }

        else
        {
            lblMessage.Text = "Done!";
        }

Answer 1

代码示例：

public partial class BackgroundWorkerSample : Form
{
    private BackgroundWorker work = null;
    public string CustomMessage { get; set; }
    public BackgroundWorkerSample()
    {
        InitializeComponent();

        work = new BackgroundWorker();
        work.WorkerSupportsCancellation = true;
        work.WorkerReportsProgress = true;
        work.DoWork += worker_DoWork;
        work.ProgressChanged += worker_ProgressChanged;
        work.RunWorkerCompleted += worker_RunWorkerCompleted;
    }

    private void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        if (e.Cancelled)
        {
            lblStatus.ForeColor = Color.Red;
            lblStatus.Text = CustomMessage;
        }
        else
        {
            lblStatus.ForeColor = Color.Green;
            lblStatus.Text = $"Result is : {e.Result}";
        }
    }

    private void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        lblStatus.Text = $"Calculating result... ({ e.ProgressPercentage }%)";
    }

    private void worker_DoWork(object sender, DoWorkEventArgs e)
    {
        for (int i = 0; i <= 100; i++)
        {
            if (work.CancellationPending == true)
            {
                e.Cancel = true;
                return;
            }
            work.ReportProgress(i);
            System.Threading.Thread.Sleep(250);
        }
        e.Result = 42;
    }

    private void btnStart_Click(object sender, EventArgs e)
    {
        work.RunWorkerAsync();
    }

    private void btnCancel_Click(object sender, EventArgs e)
    {
        CustomMessage = "Calculation cancelled by user";
        work.CancelAsync();
    }
}

如您所见，CustomMessage 被定义为 class 成员，而不是 DoWork 中的局部变量，因此它在表单中的任何位置都可用。

请注意我对 C# 6 内插字符串的用法 ;-)

干杯

后台工作者自定义取消消息

Background worker Custom cancel message

c#

backgroundworker