如何在PowerShell作业中调用类对象？遇类型未找到错误

我创建了Test PowerShell类，计划通过后台并行作业创建该类对象并执行类中的方法。编写相关代码后，作业显示完成但未达预期，查看作业详情发现每个作业均报错：无法找到[Test]类型，以及无法找到ComputerName属性。

原代码 #

class Test {

    [String]$ComputerName
    
    
    [String]TestMrParameter() {

        if ($this.ComputerName -eq 'jhon'){throw "Bad thing happened"}
        
        return $this.ComputerName 

    }
}

$names = @('david', 'jhon', 'mark','tent')
$jobs = [System.Collections.ArrayList]@()

function TestMrParameter2 {
    param (
        [String]$name
    )
    [Test]$obj = [Test]::new()
    $obj.ComputerName = $name
    Write-Host $name + "TestMrParameter2 Function Reached!!!"
    $output=$obj.TestMrParameter()
    Write-Host "Output of the Test class is" + $output
}


foreach ($name in $names) {

    $out = Start-Job -ScriptBlock ${Function:TestMrParameter2} -ArgumentList $name
    $jobs.Add($out) | out-null

}

错误信息 #

Unable to find type [Test].
    + CategoryInfo          : InvalidOperation: (Test:TypeName) [], RuntimeException
    + FullyQualifiedErrorId : TypeNotFound
    + PSComputerName        : localhost
 
The property 'ComputerName' cannot be found on this object. Verify that the property exists and can 
be set.
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : PropertyNotFound
    + PSComputerName        : localhost

原因分析 #

PowerShell后台作业（Start-Job）会启动独立的子运行会话，当前会话中定义的类不会自动同步到子会话。你仅传递了函数TestMrParameter2，但函数依赖的Test类在子会话中未定义，因此会触发类型找不到的错误；后续的属性找不到错误是因为类不存在，对象创建失败导致的。

解决方案 #

方法1：通过初始化脚本在作业中加载类 #

将Test类的定义放到作业的初始化脚本中，确保作业启动时先加载类：

$names = @('david', 'jhon', 'mark','tent')
$jobs = [System.Collections.ArrayList]@()

# 初始化脚本：作业启动时加载Test类
$initScript = {
    class Test {
        [String]$ComputerName
        
        [String]TestMrParameter() {
            if ($this.ComputerName -eq 'jhon'){throw "Bad thing happened"}
            return $this.ComputerName 
        }
    }
}

function TestMrParameter2 {
    param (
        [String]$name
    )
    [Test]$obj = [Test]::new()
    $obj.ComputerName = $name
    # 修正字符串拼接方式，避免输出多余的+符号
    Write-Host "$name TestMrParameter2 Function Reached!!!"
    try {
        $output = $obj.TestMrParameter()
        Write-Host "Output of the Test class is $output"
        # 返回结果方便后续获取
        return $output
    }
    catch {
        Write-Error $_
        return $_
    }
}

foreach ($name in $names) {
    $out = Start-Job -InitializationScript $initScript -ScriptBlock ${Function:TestMrParameter2} -ArgumentList $name
    $jobs.Add($out) | Out-Null
}

# 等待所有作业完成并接收结果
$jobs | Wait-Job | Receive-Job

方法2：将类定义保存为脚本文件导入 #

如果类定义较复杂，可将其保存为单独的脚本文件（如TestClass.ps1），再在作业初始化时导入：

TestClass.ps1内容：

class Test {
    [String]$ComputerName
    
    [String]TestMrParameter() {
        if ($this.ComputerName -eq 'jhon'){throw "Bad thing happened"}
        return $this.ComputerName 
    }
}

主脚本修改为：

$names = @('david', 'jhon', 'mark','tent')
$jobs = [System.Collections.ArrayList]@()

function TestMrParameter2 {
    param (
        [String]$name
    )
    [Test]$obj = [Test]::new()
    $obj.ComputerName = $name
    Write-Host "$name TestMrParameter2 Function Reached!!!"
    try {
        $output = $obj.TestMrParameter()
        Write-Host "Output of the Test class is $output"
        return $output
    }
    catch {
        Write-Error $_
        return $_
    }
}

foreach ($name in $names) {
    # 替换为实际的TestClass.ps1文件路径
    $out = Start-Job -InitializationScript { . "C:\scripts\TestClass.ps1" } -ScriptBlock ${Function:TestMrParameter2} -ArgumentList $name
    $jobs.Add($out) | Out-Null
}

$jobs | Wait-Job | Receive-Job

额外说明：原代码中Write-Host用+拼接字符串会导致输出格式错误，已修正为双引号插值的方式，避免输出多余的+符号。

内容的提问来源于stack exchange，提问作者Chethiya Amarasinghe