在运行背景与委托工作时，如何处理控制启用/禁用选项

Question

on button_click事件，我有一个需要很长时间的查询。所以我在背景工作者上运行它

     private void btnGenerate_Click(object sender, EventArgs e)
        {
            btnGenerate.Enabled = false;
            BackgroundWorker worker = new BackgroundWorker();
            worker.DoWork += delegate (object s, DoWorkEventArgs args)
            {
                Data = DataLoader.GetData(Environment.UserName); // stored procedure execution 
                if (Data != null)
                {
                    GenerateExcel(Data);
                    GenerateSingleExcel(Data);
                } 
            };    
            worker.RunWorkerCompleted += delegate (object s, RunWorkerCompletedEventArgs args)
            {
                progressBar1.Visible = false;// ProgressBarStyle.Marquee 
                btnGenerate.Enabled = true;   
            };    
            worker.RunWorkerAsync();
}

我的问题是，我需要设置

btngenerate.enable = false;

在button_click处。并在执行后启用。

我在RunWorkerCompleted中尝试了它，但它显示

'跨线程操作无效：从其创建的线程以外的线程访问的" btngenerate"。

任何建议都会有所帮助。

Answer 1

您的主要问题是BackgroundWorker的事件是在工作人员的线程上执行的，而不是UI线程。但是只能从UI线程访问UI元素。

要解决它，我建议使用async/await而不是BackgroundWorker：

// declare as async
private async void btnGenerate_Click(object sender, EventArgs e)
{
    btnGenerate.Enabled = false;
    Data = await Task.Run(() => {
                var data = DataLoader.GetData(Environment.UserName); // stored procedure execution 
                if (data != null)
                {
                    GenerateExcel(Data);
                    GenerateSingleExcel(Data);
                }
                return data; // as suggested by Vlad, don't set Data on this thread
            });    
    // this is now executed back on the UI thread
    progressBar1.Visible = false;// ProgressBarStyle.Marquee 
    btnGenerate.Enabled = true;   
}

如果DataLoader提供异步的GetDataAsync，甚至不需要Task.Run()。

---

如果无法（无论出于何种原因）async，则您的RunWorkerCompleted处理程序应使用Invoke或BeginInvoke：

worker.RunWorkerCompleted += OnRunWorkerCompleted;
//...
public void OnRunWorkerCompleted(object s, RunWorkerCompletedEventArgs args)
{
    if (InvokeRequired)
    {
        // not on the UI thread - use (Begin-)Invoke
        BeginInvoke(new RunWorkerCompletedEventHandler(OnRunWorkerCompleted), s, args);
        return;
    }
    // now we're on the UI thread
    progressBar1.Visible = false;// ProgressBarStyle.Marquee 
    btnGenerate.Enabled = true;   
}