c# - 从事件处理程序报告 Powershell 进度

Question

我用 C# 编写了一个 cmdlet，它充当繁重/长时间运行的同步操作的包装器。该方法(其他人的代码)通过事件处理程序报告此长时间运行操作期间的进度百分比，我想将这些连接到 powershell 的标准 WriteProgress 方法以获得 pretty-print 进度条.但是，我收到以下错误消息:

WriteObject 和 WriteError 方法不能从 BeginProcessing、ProcessRecord 和 EndProcessing 方法的覆盖之外调用，它们只能在同一线程内调用。

这是我的代码:

overrride void ProcessRecord()
{
    LongRunningOperation op = new LongRunningOperation();
    op.ProgressChanged += ProgressUpdate;
    op.Execute();
    op.ProgressChanged -= ProgressUpdate;
}

void ProgressUpdate(object sender, ProgressChangeEventArgs e)
{
   ProgressRecord progress = new ProgressRecord(activityId: 1, activity: "Moving data", statusDescription: "Current operation");
   progress.PercentComplete = e.ProgressPercentage;
   WriteProgress(progress);
}

有人能发现我做错了什么吗？

更新:看起来事件处理程序是从不同于 ProcessRecord() 的线程触发的。如何将我需要的信息返回到与 ProcessRecord() 相同的线程中？

Answer 1

您需要手动编码 ProgressChanged事件处理程序返回到 PowerShell 管道线程。这可以通过应用生产者-消费者模式来完成，其中 ProgressChanged事件处理程序将成为生产者，PowerShell 管道线程中的事件循环将成为消费者。在 BlockingCollection<T> 的支持下可以轻松实现在 .NET Framework 4.0 中引入:

overrride void ProcessRecord() {
    Task longRunningOperation;
    using(BlockingCollection<ProgressRecord> queue = new BlockingCollection<ProgressRecord>()) {
        //offload LongRunningOperation to different thread to keep control on PowerShell pipeline thread
        longRunningOperation=Task.Run(() => {
            try {
                //replace EventHandler<ProgressChangeEventArgs> with ProgressChanged type
                EventHandler<ProgressChangeEventArgs> handler =
                    //implemented as anonymous method to capture queue local variable
                    (object sender, ProgressChangeEventArgs e) => {
                        ProgressRecord progress = new ProgressRecord(activityId: 1, activity: "Moving data", statusDescription: "Current operation");
                        progress.PercentComplete = e.ProgressPercentage;
                        //queue ProgressRecord for processing in PowerShell pipeline thread
                        queue.Add(progress);
                    }
                LongRunningOperation op = new LongRunningOperation();
                op.ProgressChanged += handler;
                op.Execute();
                op.ProgressChanged -= handler;
            } finally {
                queue.CompleteAdding();
            }
        });
        //event loop
        for(;;) {
            ProgressRecord progress;
            if(!queue.TryTake(out progress, Timeout.Infinite)) {
                break;
            }
            WriteProgress(progress);
        }
    }
    //get any exception from LongRunningOperation
    longRunningOperation.GetAwaiter().GetResult();
}