在什么情况下后台工作者不会运行DoWork方法来完成？

发布于 2024-08-12 15:31:08 字数 664 浏览 8 评论 0原文

我在表单上有一个后台工作人员，并且在其中编写了一些长时间运行的数据库交互。

当我单击表单上的按钮时，将运行以下内容：

if (!bwFind.IsBusy)
    bwFind.RunWorkerAsync(param);

其中 bwFind 是 BackgroundWorker，param 是 DevExpress CriteriaOperator。

我在 Progress_Changed 事件处理程序中更新进度条。

我在 RunWorkerCompleted 事件处理程序中执行以下操作：

dataGrid.DataSource = this.dataObject;
dataGrid.Refresh();
label1.Text = this.dataObject.Count.ToString(); // problem appears here

问题是，我在指定的行处收到 Null Ref Exception，但我在 DoWork 方法的末尾实例化了该对象。

我知道 DoWork 没有运行，因为如果我在使用它之前进行空检查，再次按下表单上的按钮...它就会运行，并且一切都按预期工作。

也许我没有正确使用BackgroundWorker，但每当我使用该组件时，这种情况经常发生。

原文

I've got a background worker on a form and I've written some long running DB interaction in it.

When I click a button on my form, the following runs:

if (!bwFind.IsBusy)
    bwFind.RunWorkerAsync(param);

Where bwFind is the BackgroundWorker and param is a DevExpress CriteriaOperator.

I update a progressbar in the Progress_Changed event handler.

And I do the following in the RunWorkerCompleted event handler:

dataGrid.DataSource = this.dataObject;
dataGrid.Refresh();
label1.Text = this.dataObject.Count.ToString(); // problem appears here

Problem is, that I get a Null Ref Exception at the line noted, however I instantiate that object, at the end of the DoWork method.

I know that DoWork isn't running, cause if I do a null-check before using it, press the button on the form a second time... it runs, and all works as expected.

Maybe I'm not using the BackgroundWorker correctly, but this happens very often whenever I use the component.

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

被翻牌 2024-08-19 15:31:08

实现 RunWorkerCompleted 有一个特定的模式。

首先，检查 e.Error （例外）
其次，检查取消（如果支持
）最后，接受结果

通常将结果分配给 DoWork 中的 e.Result 进行传输它是 RunWorkerCompleted，但您为此使用类成员。确保 this.dataObject 的使用是线程安全的。

   void backgroundWorker1_RunWorkerCompleted(object sender, 
        RunWorkerCompletedEventArgs e)
    {
        // First, handle the case where an exception was thrown.
        if (e.Error != null)
        {
            label1.Text = e.Error.Message;
        }
        else if (e.Cancelled)
        {
            label1.Text = "Canceled";
        }
        else
        {
            // Finally, handle the case where the operation 
            // succeeded.
            label1.Text = this.dataObject.Count.ToString();
        }

        // update UI for Thread completed
    }

There is a specific pattern for implementing RunWorkerCompleted.

First, Check e.Error (Exceptions)
Second, Check for Cancelation, if supported
And finally, Accept result

And you normally assign the result to e.Result in DoWork to transfer it to RunWorkerCompleted, but you use a class member for that. Make sure the use of this.dataObject is thread-safe.

   void backgroundWorker1_RunWorkerCompleted(object sender, 
        RunWorkerCompletedEventArgs e)
    {
        // First, handle the case where an exception was thrown.
        if (e.Error != null)
        {
            label1.Text = e.Error.Message;
        }
        else if (e.Cancelled)
        {
            label1.Text = "Canceled";
        }
        else
        {
            // Finally, handle the case where the operation 
            // succeeded.
            label1.Text = this.dataObject.Count.ToString();
        }

        // update UI for Thread completed
    }

回复收藏 0 原文