Powershell管道属性绑定失败

Question

我遇到了一个我搞不懂的特殊问题。我试图将Get-ADUser -Identity Test-User -Property SamAccountName的值绑定到定制的cmdlet。这是我以前做过很多次的事情，但由于一些奇怪的原因，它现在已经失败了。为了降低复杂性，我编写了一个测试函数来最小化复杂性。这一职能是：

function Test-Binding{
    [cmdletbinding()]
    Param
    (
        [Parameter(Mandatory=$true,
                   ValueFromPipelineByPropertyName=$True)]
        [Alias("SamAccountName")]
        [string]
        $Identity
    )

    return $Identity
}

在执行Get-ADUser -Identity Test-user | Test-Binding时，我会得到以下错误：

Test-Binding : Cannot bind argument to parameter 'Identity' because it is an empty string.
At line:1 char:76
+ Trace-Command parameterbinding -Expression {Get-ADUser -Identity Test-User | Test- ...
+                                                                            ~~~~~
    + CategoryInfo          : InvalidData: (CN=Test-User...,DC=contoso,DC=com:PSObject) [Test-Binding], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationErrorEmptyStringNotAllowed,Test-Binding

在查看了我的代码并查看了之前成功的脚本之后，我的下一步是运行跟踪。在跟踪中，绑定在第一次尝试中是成功的，但是powershell随后尝试继续将其绑定到其他输入值，直到它退出为止。这是垃圾场：

DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Get-ADUser]
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Get-ADUser]
DEBUG: ParameterBinding Information: 0 : BIND cmd line args to DYNAMIC parameters.
DEBUG: ParameterBinding Information: 0 :     DYNAMIC parameter object: [Microsoft.ActiveDirectory.Management.Commands.GetADUserParameterSet]
DEBUG: ParameterBinding Information: 0 :     BIND NAMED args to DYNAMIC parameters
DEBUG: ParameterBinding Information: 0 :         BIND arg [Test-User] to parameter [Identity]
DEBUG: ParameterBinding Information: 0 :             COERCE arg to [Microsoft.ActiveDirectory.Management.ADUser]
DEBUG: ParameterBinding Information: 0 :                 Trying to convert argument value from System.String to Microsoft.ActiveDirectory.Management.ADUser
DEBUG: ParameterBinding Information: 0 :                 CONVERT arg type to param type using LanguagePrimitives.ConvertTo
DEBUG: ParameterBinding Information: 0 :                 CONVERT SUCCESSFUL using LanguagePrimitives.ConvertTo: [Test-User]
DEBUG: ParameterBinding Information: 0 :             Executing VALIDATION metadata: [Microsoft.ActiveDirectory.Management.Commands.ValidateNotNullOrEmptyADEntityAttribute
]
DEBUG: ParameterBinding Information: 0 :             Executing VALIDATION metadata: [System.Management.Automation.ValidateNotNullAttribute]
DEBUG: ParameterBinding Information: 0 :             BIND arg [Test-User] to param [Identity] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 :     BIND POSITIONAL args to DYNAMIC parameters
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Get-ADUser]
DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Test-Binding]
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Test-Binding]
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Test-Binding]
DEBUG: ParameterBinding Information: 0 :     BIND arg [] to parameter [Identity]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: 
DEBUG: ParameterBinding Information: 0 :         COERCE arg to [System.String]
DEBUG: ParameterBinding Information: 0 :             Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :         BIND arg [] to param [Identity] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : BIND PIPELINE object to parameters: [Test-Binding]
DEBUG: ParameterBinding Information: 0 :     PIPELINE object TYPE = [Microsoft.ActiveDirectory.Management.ADUser]
DEBUG: ParameterBinding Information: 0 :     RESTORING pipeline parameter's original values
DEBUG: ParameterBinding Information: 0 :     Parameter [Identity] PIPELINE INPUT ValueFromPipelineByPropertyName NO COERCION
DEBUG: ParameterBinding Information: 0 :     BIND arg [Microsoft.ActiveDirectory.Management.ADPropertyValueCollection] to parameter [Identity]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: Microsoft.ActiveDirectory.Management.ADPropertyValueCollection
DEBUG: ParameterBinding Information: 0 :         BIND arg [Microsoft.ActiveDirectory.Management.ADPropertyValueCollection] to param [Identity] SKIPPED
DEBUG: ParameterBinding Information: 0 :     Parameter [Identity] PIPELINE INPUT ValueFromPipelineByPropertyName WITH COERCION
DEBUG: ParameterBinding Information: 0 :     BIND arg [Microsoft.ActiveDirectory.Management.ADPropertyValueCollection] to parameter [Identity]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: 
DEBUG: ParameterBinding Information: 0 :         COERCE arg to [System.String]
DEBUG: ParameterBinding Information: 0 :             Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :         ERROR: Argument cannot be an empty string
DEBUG: ParameterBinding Information: 0 : BIND PIPELINE object to parameters: [Out-Default]
DEBUG: ParameterBinding Information: 0 :     PIPELINE object TYPE = [System.Management.Automation.ErrorRecord]
DEBUG: ParameterBinding Information: 0 :     RESTORING pipeline parameter's original values
DEBUG: ParameterBinding Information: 0 :     Parameter [InputObject] PIPELINE INPUT ValueFromPipeline NO COERCION
DEBUG: ParameterBinding Information: 0 :     BIND arg [Cannot bind argument to parameter 'Identity' because it is an empty string.] to parameter [InputObject]
DEBUG: ParameterBinding Information: 0 :         BIND arg [Cannot bind argument to parameter 'Identity' because it is an empty string.] to param [InputObject] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Out-Default]
DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Out-LineOutput]
DEBUG: ParameterBinding Information: 0 :     BIND arg [Microsoft.PowerShell.Commands.Internal.Format.ConsoleLineOutput] to parameter [LineOutput]
DEBUG: ParameterBinding Information: 0 :         COERCE arg to [System.Object]
DEBUG: ParameterBinding Information: 0 :             Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :         BIND arg [Microsoft.PowerShell.Commands.Internal.Format.ConsoleLineOutput] to param [LineOutput] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Out-LineOutput]
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Out-LineOutput]
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : BIND PIPELINE object to parameters: [Out-LineOutput]
DEBUG: ParameterBinding Information: 0 :     PIPELINE object TYPE = [System.Management.Automation.ErrorRecord]
DEBUG: ParameterBinding Information: 0 :     RESTORING pipeline parameter's original values
DEBUG: ParameterBinding Information: 0 :     Parameter [InputObject] PIPELINE INPUT ValueFromPipeline NO COERCION
DEBUG: ParameterBinding Information: 0 :     BIND arg [Cannot bind argument to parameter 'Identity' because it is an empty string.] to parameter [InputObject]
DEBUG: ParameterBinding Information: 0 :         BIND arg [Cannot bind argument to parameter 'Identity' because it is an empty string.] to param [InputObject] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [out-lineoutput]
DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Format-Default]
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Format-Default]
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Format-Default]
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : BIND PIPELINE object to parameters: [Format-Default]
DEBUG: ParameterBinding Information: 0 :     PIPELINE object TYPE = [System.Management.Automation.ErrorRecord]
DEBUG: ParameterBinding Information: 0 :     RESTORING pipeline parameter's original values
DEBUG: ParameterBinding Information: 0 :     Parameter [InputObject] PIPELINE INPUT ValueFromPipeline NO COERCION
DEBUG: ParameterBinding Information: 0 :     BIND arg [Cannot bind argument to parameter 'Identity' because it is an empty string.] to parameter [InputObject]
DEBUG: ParameterBinding Information: 0 :         BIND arg [Cannot bind argument to parameter 'Identity' because it is an empty string.] to param [InputObject] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [format-default]
DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 :     BIND arg [1] to parameter [Version]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [Microsoft.PowerShell.Commands.SetStrictModeCommand+ArgumentToVersionTransformationAt
tribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: 1.0
DEBUG: ParameterBinding Information: 0 :         COERCE arg to [System.Version]
DEBUG: ParameterBinding Information: 0 :             Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :         Executing VALIDATION metadata: [Microsoft.PowerShell.Commands.SetStrictModeCommand+ValidateVersionAttribute]
DEBUG: ParameterBinding Information: 0 :         BIND arg [1.0] to param [Version] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : CALLING EndProcessing
DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 :     BIND arg [1] to parameter [Version]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [Microsoft.PowerShell.Commands.SetStrictModeCommand+ArgumentToVersionTransformationAt
tribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: 1.0
DEBUG: ParameterBinding Information: 0 :         COERCE arg to [System.Version]
DEBUG: ParameterBinding Information: 0 :             Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :         Executing VALIDATION metadata: [Microsoft.PowerShell.Commands.SetStrictModeCommand+ValidateVersionAttribute]
DEBUG: ParameterBinding Information: 0 :         BIND arg [1.0] to param [Version] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : CALLING EndProcessing
DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 :     BIND arg [1] to parameter [Version]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [Microsoft.PowerShell.Commands.SetStrictModeCommand+ArgumentToVersionTransformationAt
tribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: 1.0
DEBUG: ParameterBinding Information: 0 :         COERCE arg to [System.Version]
DEBUG: ParameterBinding Information: 0 :             Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :         Executing VALIDATION metadata: [Microsoft.PowerShell.Commands.SetStrictModeCommand+ValidateVersionAttribute]
DEBUG: ParameterBinding Information: 0 :         BIND arg [1.0] to param [Version] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : CALLING EndProcessing
DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 :     BIND arg [1] to parameter [Version]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [Microsoft.PowerShell.Commands.SetStrictModeCommand+ArgumentToVersionTransformationAt
tribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: 1.0
DEBUG: ParameterBinding Information: 0 :         COERCE arg to [System.Version]
DEBUG: ParameterBinding Information: 0 :             Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :         Executing VALIDATION metadata: [Microsoft.PowerShell.Commands.SetStrictModeCommand+ValidateVersionAttribute]
DEBUG: ParameterBinding Information: 0 :         BIND arg [1.0] to param [Version] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Set-StrictMode]
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : CALLING EndProcessing
Test-Binding : Cannot bind argument to parameter 'Identity' because it is an empty string.
At line:1 char:76
+ Trace-Command parameterbinding -Expression {Get-ADUser -Identity Test-User | Test- ...
+                                                                            ~~~~~
    + CategoryInfo          : InvalidData: (CN=Walter Kerce...,DC=contoso,DC=com:PSObject) [Test-Binding], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationErrorEmptyStringNotAllowed,Test-Binding

DEBUG: ParameterBinding Information: 0 : CALLING EndProcessing
DEBUG: ParameterBinding Information: 0 : CALLING EndProcessing

我的目标是理解为什么这种绑定在这种情况下失败。

编辑：

这不是一个副本，因为我没有使用$null返回。

Answer 1

不幸的是，这是AD中的一个已知问题--如果您要求AD生成的对象具有它没有的属性，它将自动生成一个$null值，而不是正确地返回属性不存在，这将允许参数绑定继续并获得正确的值。

您可以看到有关此这里的Microsoft项。

我看到的唯一解决办法是根据AD对象使用的确切属性名称和别名命名函数中的参数。例如，如果我想让Get通过管道连接到参数DNSHostName，我通常必须用ComputerName的别名命名参数。