在从控制面板卸载第三方应用程序期间，我收到此错误不能在空值表达式上调用方法 PowerShell

问题描述

我有脚本可以通过 PowerShell 从控制面板卸载 Veeam 软件。在卸载最后一个 Veeam 组件期间，我收到以下错误：

You Cannot call a method on a null-valued expression PowerShell : line 15 char:1
+ $console.Uninstall()
+ CategoryInfo         : InvalidOperation: (:) [],RuntimeException
+FullyQualifiedErrorId : InvokeMethodonNull

我不知道，专家帮我解决。我在等你的回复。我在下面附上了我的脚本。

function uninstallvm
{
$veeamConsole = 'Veeam Backup & Replication Console'
$objects = Get-WmiObject -Class win32_product
$veeamComponents = $objects | where {$_.Name -like 'Veeam*' -and $_.Name -ne $veeamConsole}
foreach ($object in $veeamComponents) {
  Write-Output "Uninstalling $($object.Name)"
  $object.Uninstall()
}
Start-Sleep -Seconds 5
$console = $objects | where {$_.Name -eq $veeamConsole}
Write-Output "Uninstalling $($console.Name)"
$console.Uninstall() 
}
uninstallvm

解决方法

您收到该错误的原因是在此之后：

$console = $objects | where {$_.Name -eq $veeamConsole}

您的 $console 变量为 $null，表示没有找到具有 Name 属性的对象 等于 Veeam备份和复制控制台：

PS /> $null.Uninstall()
You cannot call a method on a null-valued expression.
At line:1 char:1
+ $null.Uninstall()
+ ~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [],RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

这可以通过在尝试调用 uninstall 方法之前添加条件来轻松解决。

function uninstallvm
{
    $veeamConsole = 'Veeam Backup & Replication Console'
    $objects = Get-WmiObject -Class win32_product
    $veeamComponents = $objects | where {$_.Name -like 'Veeam*' -and $_.Name -ne $veeamConsole}
    
    foreach ($object in $veeamComponents)
    {
        Write-Output "Uninstalling $($object.Name)"
        $object.Uninstall()
    }
    
    Start-Sleep -Seconds 5
    
    $console = $objects | where {$_.Name -eq $veeamConsole}
    
    if(-not $console)
    {
        return "No object found with name: $veeamConsole"
    }

    Write-Output "Uninstalling $($console.Name)"
    $console.Uninstall() 
}

uninstallvm

get-wmiobject powershell uninstallation