C# 异步/等待方法和异常处理的最佳实践

我必须处理一些使用异步函数不能正确运行的旧东西，由于我对这个概念的理解有限，我正在努力寻找处理以下问题的最佳方法

我有一个按钮，单击该按钮将执行一个长时间运行的任务（解压缩大型ZIP存档，需要几分钟）。其

命令

执行方法定义如下：

private async void Import()
{
    // some stuff
    tokenSource = new CancellationTokenSource();
    IProgress<ProgressReport> progress = new Progress<ProgressReport>(data => Report(data));

    try
    {
        await Task.Run(() =>
        {
            Backup(tokenSource.Token, progress);
            Unzip(tokenSource.Token, progress);
        });
    }
    catch(Exception)
    {
        // do some rollback operation
    }

private void Backup(CancellationToken token, IProgress<ProgressReport> progress)
{
token.ThrowIfCancellationRequested();

    var parent = Path.GetFullPath(Path.Combine(Paths.DataDirectory, ".."));
    if (!Directory.Exists(parent))
    {
        progress.Report(new ProgressReport(Level.Info, string.Format(
                "Root Directory ({0}) does not exist; Creating it.", parent)));
        Directory.CreateDirectory(parent);
        return;
    }

    if (!Directory.Exists(Paths.DataDirectory))
    {
        progress.Report(new ProgressReport(Level.Info, string.Format(
                "Data Directory ({0}) does not exist; nothing to backup.", Paths.DataDirectory)));
        return;
    }

    // Generate a name for the backup           
    try
    {
        progress.Report(new ProgressReport(Level.Info, string.Format(
                "Renaming source Data Directory ({0}) to a temporary name.", Paths.DataDirectory)));

        var temp = Path.Combine(parent, Guid.NewGuid().ToString("N"));
        Directory.Move(Paths.DataDirectory, temp);
        // Success, let's store the backupFolder in a class field
        backupFolder = temp;

        progress.Report(new ProgressReport(Level.Info, string.Format(
                "Source Data Directory ({0}) successfully renamed to {1}.", Paths.DataDirectory, backupFolder)));

        token.ThrowIfCancellationRequested();
    }
    catch (OperationCanceledException)
    {
        progress.Report(new ProgressReport(Level.Warn, "Cancelling Import Operation."));
        throw;
    }
    catch (Exception ex)
    {
        // some stuff then throw Exception to bubble-up
        throw;
    }
}

try
{
    await Backup(tokenSource.Token, progress);
    await Unzip(tokenSource.Token, progress);
}

private async Task Backup(CancellationToken token, IProgress<ProgressReport> progress)
{
    // Same logic
    Task.Delay(1000);
}

private async Task Unzip(CancellationToken token, IProgress<ProgressReport> progress)
{
    // Same logic
    Task.Delay(1000);
}

我的方法定义如下：

private async void Import()
{
    // some stuff
    tokenSource = new CancellationTokenSource();
    IProgress<ProgressReport> progress = new Progress<ProgressReport>(data => Report(data));

    try
    {
        await Task.Run(() =>
        {
            Backup(tokenSource.Token, progress);
            Unzip(tokenSource.Token, progress);
        });
    }
    catch(Exception)
    {
        // do some rollback operation
    }

private void Backup(CancellationToken token, IProgress<ProgressReport> progress)
{
token.ThrowIfCancellationRequested();

    var parent = Path.GetFullPath(Path.Combine(Paths.DataDirectory, ".."));
    if (!Directory.Exists(parent))
    {
        progress.Report(new ProgressReport(Level.Info, string.Format(
                "Root Directory ({0}) does not exist; Creating it.", parent)));
        Directory.CreateDirectory(parent);
        return;
    }

    if (!Directory.Exists(Paths.DataDirectory))
    {
        progress.Report(new ProgressReport(Level.Info, string.Format(
                "Data Directory ({0}) does not exist; nothing to backup.", Paths.DataDirectory)));
        return;
    }

    // Generate a name for the backup           
    try
    {
        progress.Report(new ProgressReport(Level.Info, string.Format(
                "Renaming source Data Directory ({0}) to a temporary name.", Paths.DataDirectory)));

        var temp = Path.Combine(parent, Guid.NewGuid().ToString("N"));
        Directory.Move(Paths.DataDirectory, temp);
        // Success, let's store the backupFolder in a class field
        backupFolder = temp;

        progress.Report(new ProgressReport(Level.Info, string.Format(
                "Source Data Directory ({0}) successfully renamed to {1}.", Paths.DataDirectory, backupFolder)));

        token.ThrowIfCancellationRequested();
    }
    catch (OperationCanceledException)
    {
        progress.Report(new ProgressReport(Level.Warn, "Cancelling Import Operation."));
        throw;
    }
    catch (Exception ex)
    {
        // some stuff then throw Exception to bubble-up
        throw;
    }
}

try
{
    await Backup(tokenSource.Token, progress);
    await Unzip(tokenSource.Token, progress);
}

private async Task Backup(CancellationToken token, IProgress<ProgressReport> progress)
{
    // Same logic
    Task.Delay(1000);
}

private async Task Unzip(CancellationToken token, IProgress<ProgressReport> progress)
{
    // Same logic
    Task.Delay(1000);
}

专用异步任务备份（CancellationToken令牌，IProgress进程）
{
//同样的逻辑
任务延迟（1000）；
}
专用异步任务解压缩（CancellationToken令牌，IProgress进程）
{
//同样的逻辑
任务延迟（1000）；
}

---

现在异常很好地出现在

Import

方法中，但是UI在整个作业完成时间内都是冻结的，就像作业是由UI线程处理的一样。有什么不对劲吗？

多亏了@i3arnon的评论，我终于实现了我想要的。 以下是我的电话是如何改变的：

await Task.Run(async () =>
{
    await Backup(tokenSource.Token, progress);
    await Unzip(tokenSource.Token, progress);
});

而且这两个函数仍然声明为

专用异步任务

---

这样，由于

任务，作业在后台运行。运行

，这样UI就不会冻结，异常就会正确出现。

您是否仍在使用

任务。运行

？看起来您将方法标记为

异步

，但它们是同步的，而不是异步的，但由于您没有显示它们的实现，具体说来，你做错了什么，无从得知。我用方法实现编辑了我的文章。不，我不再使用

任务。再运行
。@BastienM。如果希望这些方法在后台运行，则需要
Task.run
@BastienM。这是无关的。您可以使用
任务。运行
。在它内部调用一个异步方法并等待返回的任务。在这种情况下，异常将“冒泡”。