如何在后台运行异步表单而不会死锁

如何解决如何在后台运行异步表单而不会死锁

在后台运行异步表单而不会出现死锁

FormA（参见下面的示例）很旧，并且由于大量延迟加载EF6代码等而导致加载缓慢。我们已经设法通过一些异步方法来加快它的运行速度，这些方法允许至少在加载数据时显示表单。一直到事件处理程序为止的异步工作都很好-UNTIL：同一表单由第二个表单（FormB）在后台加载，该表单循环并为多个记录加载该表单，以便对数据进行一些检查它会加载（是的，一点都不理想，但现在不去那里）。

在异步更改之前，正在使用Thread.Start(...)开始在FormB的方法中创建FormA-现在我们一直在进行异步操作，直到启动批量更新过程的Button_Click事件处理程序为止，但是FormA现在正在占用UI线程，因此FormB直到完成所有操作后才更新任何进度指示器。

我们尝试使用Task.Run(...)创建FormA实例并完成其工作，但是我们总是在FormA的第一个await asyncMethod(...)上遇到僵局。这些异步方法的最低级别确实使用ConfigreAwait(False)，但是较高级别的原因不是，因为从数据库中检索数据后必须更新UI组件，这些UI组件必须在创建表单的同一线程上进行，并且它的控件。

FormA具有这种代码

    public partial class FormA : Form
    {
        private int _counter;

        public FormA(int counter)
        {
            InitializeComponent();

            _counter = counter;
        }

        private async void formDoWork_Load(object sender,EventArgs e)
        {
            this.Text = "Loading...";
            await Task.Delay(5000); // Various async tasks happen here
            this.Text = "Loaded";
        }

        public async Task LoadDataAsync()
        {
            this.workingLabel.Text = "Working...";
            string result = await GetDataAsync(); // Get the data but can't ConfigureAwait(false) because we need to update UI components afterwards
            this.workingLabel.Text = "Finished! " + result;
        }

        private async Task<string> GetDataAsync()
        {
            // Get the data from the database - we can ConfigureAwait(false) here because no UI components are updated at this level (in real code this would be in a separate data layer library)
            await Task.Delay(3000).ConfigureAwait(false);
            return $"Loading #{_counter}";
        }
    }

然后在FormB中我们执行以下操作：

public partial class FormB : Form
{
    public FormB()
    {
        InitializeComponent();
    }

    private async void GoButton_Click(object sender,EventArgs e)
    {
        this.GoButton.Enabled = false;
        var activeTasks = new List<Task>();

        for (int i = 0; i < 10; i++)
        {
            // Start processing form asynchronously and keep track of the task for later
            Task processTask = ProcessFormAsync(i);
            activeTasks.Add(processTask);
            this.ProgressLabel.Text = $"Started #{i}";
            await Task.Delay(1000);
        }

        // Wait for all the tasks to be finished,then update progress on UI
        await Task.WhenAll(activeTasks);

        this.ProgressLabel.Text = "Finished.";
        this.GoButton.Enabled = true;
    }

    private async Task ProcessFormAsync(int counter)
    {
        using (var newForm = new FormA(counter))
        {
            // Show the form to trigger form_Load event handler and then hide it again
            newForm.Show();
            newForm.Hide();

            // Now call the main Load function which is also async.
            await newForm.LoadDataAsync();
            newForm.Close();
        }
    }
}

除了所有内容（除了FormA.GetDataAsync之外）都在主UI线程上运行之外，其他所有方法都工作正常

AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244)  | 0 >>>
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 0 >>>
AsyncWinForms.FormA.GetDataAsync() | Main Thread(7244) | 0 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244)  | 1 >>>
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 1 >>>
AsyncWinForms.FormA.GetDataAsync() | Main Thread(7244) | 1 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244)  | 2 >>>
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 2 >>>
AsyncWinForms.FormA.GetDataAsync() | Main Thread(7244) | 2 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13984) | 0 <<<
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 0 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244)  | 3 >>>
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 3 >>>
AsyncWinForms.FormA.GetDataAsync() | Main Thread(7244) | 3 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13984) | 1 <<<
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 1 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244)  | 4 >>>
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 4 >>>
AsyncWinForms.FormA.GetDataAsync() | Main Thread(7244) | 4 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244) | 0 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13984) | 2 <<<
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 2 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244)  | 5 >>>
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 5 >>>
AsyncWinForms.FormA.GetDataAsync() | Main Thread(7244) | 5 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244) | 1 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13984) | 3 <<<
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 3 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244)  | 6 >>>
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 6 >>>
AsyncWinForms.FormA.GetDataAsync() | Main Thread(7244) | 6 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244) | 2 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13984) | 4 <<<
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 4 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244)  | 7 >>>
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 7 >>>
AsyncWinForms.FormA.GetDataAsync() | Main Thread(7244) | 7 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244) | 3 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13984) | 5 <<<
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 5 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244)  | 8 >>>
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 8 >>>
AsyncWinForms.FormA.GetDataAsync() | Main Thread(7244) | 8 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244) | 4 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13984) | 6 <<<
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 6 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244)  | 9 >>>
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 9 >>>
AsyncWinForms.FormA.GetDataAsync() | Main Thread(7244) | 9 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244) | 5 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13984) | 7 <<<
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 7 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244) | 6 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13984) | 8 <<<
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 8 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244) | 7 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13984) | 9 <<<
AsyncWinForms.FormA.LoadDataAsync() | Main Thread(7244) | 9 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244) | 8 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Main Thread(7244) | 9 <<<
The program '[17808] AsyncWinForms.exe' has exited with code 0 (0x0).

在我们的实际场景中，FormA忙于执行UI工作，这意味着在处理结束之前，FormB上的任何内容都不会更新，这违背了更新进度的目的。因此，我们尝试将其更改为在像这样的bacgkround线程上运行FormA：

Task processTask = Task.Run(async () => await ProcessForm(i).ConfigureAwait(false)));

FormB现在可以更新进度，但是FormA在任何await ...Async方法调用上都死锁。

解锁输出：

AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Worker Thread(13184)  | 0 >>>
AsyncWinForms.FormA.LoadDataAsync() | Worker Thread(13184) | 0 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 0 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Worker Thread(13184)  | 1 >>>
AsyncWinForms.FormA.LoadDataAsync() | Worker Thread(13184) | 1 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 1 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Worker Thread(13184)  | 2 >>>
AsyncWinForms.FormA.LoadDataAsync() | Worker Thread(13184) | 2 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 2 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Worker Thread(13184)  | 3 >>>
AsyncWinForms.FormA.LoadDataAsync() | Worker Thread(13184) | 3 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 3 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 0 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Worker Thread(13184)  | 4 >>>
AsyncWinForms.FormA.LoadDataAsync() | Worker Thread(13184) | 4 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 4 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(12084) | 1 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Worker Thread(13184)  | 5 >>>
AsyncWinForms.FormA.LoadDataAsync() | Worker Thread(13184) | 5 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 5 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(12084) | 2 <<<
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Worker Thread(13184)  | 6 >>>
AsyncWinForms.FormA.LoadDataAsync() | Worker Thread(13184) | 6 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(12084) | 3 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 6 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Worker Thread(11596)  | 7 >>>
AsyncWinForms.FormA.LoadDataAsync() | Worker Thread(11596) | 7 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 4 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(11596) | 7 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Worker Thread(13184)  | 8 >>>
AsyncWinForms.FormA.LoadDataAsync() | Worker Thread(13184) | 8 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(12084) | 5 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 8 >>>
AsyncWinForms.FormA.formDoWork_Load(object,System.EventArgs) | Worker Thread(11596)  | 9 >>>
AsyncWinForms.FormA.LoadDataAsync() | Worker Thread(11596) | 9 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(13184) | 6 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(11596) | 9 >>>
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(11596) | 7 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(1548) | 8 <<<
AsyncWinForms.FormA.GetDataAsync() | Worker Thread(12084) | 9 <<<
The thread 0x60c has exited with code 0 (0x0).
The thread 0x2f34 has exited with code 0 (0x0).
The thread 0x2d4c has exited with code 0 (0x0).
The thread 0x3380 has exited with code 0 (0x0).
The program '[6036] AsyncWinForms.exe' has exited with code 0 (0x0).

为什么会这样？我们看不到任何阻塞新工作线程的东西，但是每次都会死锁。我们有什么选择？

如何在后台运行异步表单而不会死锁

如何解决如何在后台运行异步表单而不会死锁

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