PowerShell脚本报错op_Addition方法未找到，求解决方案

问题场景 #

有一个PowerShell脚本在其他电脑可正常运行，仅单台电脑出现如下报错：

调用方法失败，因为[System.Object[]]不包含名为“op_Addition”的方法。
报错位置：C:\Users\stream1\Desktop\watchdog.ps1:8 字符:5
对应代码行：$wmi += (Get-WMIObject -Class Win32_PerfFormattedData_Tcpip_Netwo ...
错误类别信息：CategoryInfo : InvalidOperation: (op_Addition:String) [], RuntimeException
完全限定错误ID：FullyQualifiedErrorId : MethodNotFound

脚本代码如下：

#$ErrorActionPreference = 'SilentlyContinue'
$threshold = 6000
$timer = new-timespan -Seconds 10
$wmi = 0
$count = 0
$clock = [diagnostics.stopwatch]::StartNew()
while ($clock.elapsed -lt $timer){
    $wmi += (Get-WMIObject -Class Win32_PerfFormattedData_Tcpip_NetworkInterface | Select-Object BytesSentPerSec).BytesSentPerSec
    $count++
}

$kbytes = ($wmi/$count)  / 1kb * 8 #to kbit/s 


if($kbytes -le $threshold)
{
    Write-Output $kbytes
    Write-Host "Neustart"
    taskkill /f /im obs64.exe
    timeout /t 5
    Start-Process -FilePath "obs64.exe" -WorkingDirectory "C:\Program Files\obs-studio\bin\64bit\" --startstreaming --minimize-to-tray
}
else    
{
    Write-Output $kbytes
    Write-Host "Alles OK"
}

原因分析 #

问题核心是$wmi的类型意外转换：

• 初始$wmi = 0为数值类型
• 报错的电脑存在多个网络适配器，Get-WMIObject返回多个网卡对象，.BytesSentPerSec会生成一个数组（System.Object[]）
• 第一次执行$wmi += 数组时，PowerShell会自动将$wmi转换为数组类型
• 后续循环再执行$wmi += 数组时，会尝试对两个数组执行加法操作，但PowerShell数组不支持这种直接加法，因此抛出op_Addition方法不存在的错误

解决办法 #

方案1：累加单轮网卡发送量总和 #

每次获取网卡数据后，先计算所有网卡的BytesSentPerSec总和，再将数值累加到$wmi中，避免类型转换问题：

#$ErrorActionPreference = 'SilentlyContinue'
$threshold = 6000
$timer = new-timespan -Seconds 10
$wmi = 0
$count = 0
$clock = [diagnostics.stopwatch]::StartNew()
while ($clock.elapsed -lt $timer){
    # 计算当前所有网卡的BytesSentPerSec总和
    $currentTotal = (Get-WMIObject -Class Win32_PerfFormattedData_Tcpip_NetworkInterface | Select-Object -ExpandProperty BytesSentPerSec) | Measure-Object -Sum | Select-Object -ExpandProperty Sum
    $wmi += $currentTotal
    $count++
}

$kbytes = ($wmi/$count)  / 1kb * 8 #to kbit/s 


if($kbytes -le $threshold)
{
    Write-Output $kbytes
    Write-Host "Neustart"
    taskkill /f /im obs64.exe
    timeout /t 5
    Start-Process -FilePath "obs64.exe" -WorkingDirectory "C:\Program Files\obs-studio\bin\64bit\" --startstreaming --minimize-to-tray
}
else    
{
    Write-Output $kbytes
    Write-Host "Alles OK"
}

方案2：初始化为数组，最后统一求和 #

如果需要保留每轮的原始数据，可以将$wmi初始化为空数组，最后再计算所有数据的总和：

#$ErrorActionPreference = 'SilentlyContinue'
$threshold = 6000
$timer = new-timespan -Seconds 10
$wmi = @() # 初始化为空数组
$count = 0
$clock = [diagnostics.stopwatch]::StartNew()
while ($clock.elapsed -lt $timer){
    # 将每轮的网卡数据添加到数组中
    $wmi += (Get-WMIObject -Class Win32_PerfFormattedData_Tcpip_NetworkInterface | Select-Object -ExpandProperty BytesSentPerSec)
    $count++
}

# 计算所有数据的总和，再求平均值
$totalBytes = $wmi | Measure-Object -Sum | Select-Object -ExpandProperty Sum
$kbytes = ($totalBytes/$count)  / 1kb * 8 #to kbit/s 


if($kbytes -le $threshold)
{
    Write-Output $kbytes
    Write-Host "Neustart"
    taskkill /f /im obs64.exe
    timeout /t 5
    Start-Process -FilePath "obs64.exe" -WorkingDirectory "C:\Program Files\obs-studio\bin\64bit\" --startstreaming --minimize-to-tray
}
else    
{
    Write-Output $kbytes
    Write-Host "Alles OK"
}

额外优化建议 #

Get-WMIObject已被PowerShell官方弃用，建议替换为更兼容高效的Get-CimInstance：
将Get-WMIObject -Class Win32_PerfFormattedData_Tcpip_NetworkInterface替换为Get-CimInstance -ClassName Win32_PerfFormattedData_Tcpip_NetworkInterface

内容的提问来源于stack exchange，提问作者Thomas Geers