Timers.Timer 瘫痪脚本答案

【问题标题】：Timers.Timer paralyze scriptTimers.Timer 瘫痪脚本
【发布时间】：2021-11-18 11:08:24
【问题描述】：

我正在尝试运行this 示例：

Clear-Host
$timer = [Timers.Timer]::new()
$timer.Interval = 200
$action = {
    if($complete -eq 8){
        write-host "completed $complete" -ForegroundColor Red
        write-host "Timer stopped" -ForegroundColor Red
        $timer.stop()
        Unregister-Event thetimer
    }
}
Register-ObjectEvent -InputObject $timer -EventName elapsed `
–SourceIdentifier  thetimer -Action $action

$complete = 0
$timer.Start()

while($true){
    Write-Host "Script working: $complete" -ForegroundColor Green
    Start-Sleep -m 400
    $complete++
}

但是当定时器停止时，脚本就瘫痪了。

我做错了什么，如何解决？

【问题讨论】：

标签： .net powershell

【解决方案1】：

除非您直接在 global 范围内执行它（通过在提示符处粘贴它或通过 dot-sourcing 脚本包含它）。
- 原因是传递给Register-ObjectEvent 的-Action 参数的脚本块在动态模块 中运行，它只看到全局范围的变量，而不是任何其他调用者的变量，例如脚本的变量。
如果您确实从全局范围运行，则 挂起是由在 -Action 脚本块内调用 Unregister-Event 引起的：
- 改为从 调用者的范围调用它（即从调用 Register-ObjectEvent 的同一范围）。
- 当从-Action 脚本块内部调用代码时挂起（至少发生在 PowerShell 7.1，在撰写本文时的最新版本）应该被视为一个 错误;在调用Unregister-Event 时有更多事件待处理，这似乎会发生；该问题已在GitHub issue #16154 中报告

以下是一个独立的工作示例，您也可以从脚本中调用它：

$timer = [Timers.Timer]::new()
$timer.Interval = 200

$action = {
  # Note: This script block generally does NOT see the caller's variables.
  $timer = $Event.Sender  # originating timer object
  $counter = $Event.MessageData.Value # the variable object passed to -MessageData
  # Note: Since you're only *getting* and *integer* value, you needn't worry
  #       about thread synchronization.
  if ($timer.Enabled -and $counter -ge 8) { 
      write-host "completed $counter" -ForegroundColor Red
      write-host "Timer stopped" -ForegroundColor Red
      # Refer to the originating timer object with $Event.Sender or $args[0]
      $timer.stop()
      # Do NOT try to call Unregister-Event here - it'll cause a hang.
  }
}

# Initialize the counter variable.
$complete = 0

# Get the variable as a variable *object* that can be passed to the -Action
# script block with -MessageData.
$counterVarObject = Get-Variable complete

# Register the event and pass the variable object with -MessageData.
$null = Register-ObjectEvent -InputObject $timer -EventName elapsed `
                             –SourceIdentifier thetimer `
                             -Action $action -MessageData $counterVarObject

$timer.Start()

try {
  while ($timer.Enabled) { # Loop until the timer stops.
      Write-Host "Script working: $complete" -ForegroundColor Green
      Start-Sleep -m 400
      $complete++
  }
}
finally { # This is called even if the loop is aborted with Ctrl-C.
  # Unregister the event from the *caller's scope.
  Unregister-Event theTimer
}

【讨论】：