backgroundWorker取消后，重新开始就报错：此 BackgroundWorker 当前正忙，无法同时运行多个任务。

使用BackgroundWorker控件，有2个按钮buttonBegin和buttonCancel。
其他都正常，只是在用buttonBegin开始运行，然后点击buttonCancel取消后，到这里都正常。
可当再次点击buttonBegin时，就报错说：
“此 BackgroundWorker 当前正忙，无法同时运行多个任务。”查过资料，说是：this.backgroundWorker1.CancelAsync()只是将CancellationPending设置为true，并没有终止进程。
我现在想做的是，取消后，重新点击buttonBegin会重新运行。
感觉应该在buttonCancel_Click后面增加个终止该backgroundWorker1的方法，可查了半天也没找到。
代码如下：
 private void buttonBegin_Click(object sender, EventArgs e)
        {
            string[] pramlist = { "0"};
            backgroundWorker1.WorkerReportsProgress = true;
            backgroundWorker1.WorkerSupportsCancellation = true;
            backgroundWorker1.RunWorkerAsync(pramlist);
        }        private void buttonCancel_Click(object sender, EventArgs e)
        {
            this.backgroundWorker1.CancelAsync();
            buttonCancel.Enabled = false;
        }        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            BackgroundWorker worker = sender as BackgroundWorker;
            string[] pramlist = (string[])e.Argument;
            e.Result = DownLoad(worker, e, pramlist);
        }        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {    
            this.progressBar1.Value = e.ProgressPercentage;
            labelMsg.Text = string.Format("下载中{0}%，{1}", e.ProgressPercentage, e.UserState.ToString());
        }        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Error != null)
            {
                MessageBox.Show(e.Error.Message);
            }
            else if (e.Cancelled)
            {
                labelMsg.Text = "下载被取消！";
            }
            else
            {
                this.progressBar1.Value = 0;
                labelMsg.Text = bool.Parse(e.Result.ToString()) ? "下载成功！" : "下载失败!";
            }
           buttonCancel.Enabled = false;
        }
        private bool DownLoad(BackgroundWorker worker, DoWorkEventArgs e, string[] pramlist)
        {
            for (int i = 0; i < 100; i++)
            {
                System.Threading.Thread.Sleep(1000);                worker.ReportProgress(i, "下载开始");
            }
          
            return true;
        }

 

 

解决方案 »

1.  
2. 别用控件，你直接用class，每次用之前new个新的对象即可。
3. CancelAsync之后,BackgroundWorker.CancellationPending = true
   你要自己处理,具体如下:private bool DownLoad(BackgroundWorker worker, DoWorkEventArgs e, string[] pramlist)
           {
               for (int i = 0; i < 100; i++)
               {
                    if(worker.CancellationPending)
                   {
                      return false;
                   }        
                   System.Threading.Thread.Sleep(1000);                worker.ReportProgress(i, "下载开始");
               }
             
               return true;
           }
   其次Begin加IsBusy判断
   private void buttonBegin_Click(object sender, EventArgs e)
           {
                if(backgroundWorker1.IsBusy)
               {
                   return;
               }
               string[] pramlist = { "0"};            backgroundWorker1.WorkerReportsProgress = true;
               backgroundWorker1.WorkerSupportsCancellation = true;
               backgroundWorker1.RunWorkerAsync(pramlist);
           }
4. 需要在DoWork判断是否已经取消了，如果取消了，需要返回 
   backgroundworker有IsBusy属性，直接检测

5. 报错:此 BackgroundWorker 当前正忙，无法同时运行多个任务

   CancelAsync之后,BackgroundWorker.CancellationPending = true
   你要自己处理,具体如下:

   private bool DownLoad(BackgroundWorker worker, DoWorkEventArgs e, string[] pramlist)
           {
               for (int i = 0; i < 100; i++)
               {
                    if(worker.CancellationPending)
                   {
                      return false;
                   }
                   System.Threading.Thread.Sleep(1000);
   
                   worker.ReportProgress(i, "下载开始");
               }
   
               return true;
           }
   

   其次Begin加IsBusy判断

   private void buttonBegin_Click(object sender, EventArgs e)
           {
                if(backgroundWorker1.IsBusy)
               {
                   return;
               }
               string[] pramlist = { "0"};
   
               backgroundWorker1.WorkerReportsProgress = true;
               backgroundWorker1.WorkerSupportsCancellation = true;
               backgroundWorker1.RunWorkerAsync(pramlist);
           }