Question

有一个很好的解决方案 at Github 和 SO thread ，关于如何在PowerShell中使用等效的C＃lambda表达式。

根据示例，我设法为我的C＃片段创建了简单的工作lambda等效，如下所示：

ctx.Load(web, s => s.Id);
ctx.ExecuteQuery();
// 'ctx' is Microsoft.SharePoint.Client.ClientContext
// 'web' is ctx.Web -> Microsoft.SharePoint.Client.Web

在PowerShell中使用时→此功能正常。

Load-CSOMProperties -Object $clientContext.web -PropertyNames @("Id")
$clientContext.ExecuteQuery()

但是，我无法转换嵌套的lambda表达式，我尝试了一些变体，但无法弄清楚我错过了什么：

ctx.Load(web.Webs, w => w.Include(s => s.ServerRelativeUrl));
ctx.ExecuteQuery();
// web.Webs is WebCollection; s is Microsoft.SharePoint.Client.Web

在PowerShell中使用时

Load-CSOMProperties -ParentObject $clientContext.web -CollectionObject $clientContext.web.Webs -PropertyNames @("ServerRelativeUrl") -ParentPropertyName "Include"
$clientContext.ExecuteQuery()

我收到以下异常：


    An error occurred while enumerating through a collection: The collection has not
    been initialized. It has not been requested or the request has not been executed.
    It may need to be explicitly requested..
    At D:\Test.ps1:122 char:17
    +             if ($collectionObject -ne $null) {
    +                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
        + CategoryInfo          : InvalidOperation: (Microsoft.Share...int.Client.Web]:d__0) [], RuntimeException
        + FullyQualifiedErrorId : BadEnumeration Exception calling "Property" with "2" argument(s): "Instance property 'Include' is not defined for type 'Microsoft.SharePoint.Client.Web'"
    At D:\Test.ps1:137 char:13
    +             $collectionProperty = [System.Linq.Expressions.Expression ...
    +             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
        + FullyQualifiedErrorId : ArgumentException   Exception calling "Call" with "3" argument(s): "Value cannot be null. Parameter name: arguments"
    At D:\Test.ps1:144 char:13
    +             $callMethod = [System.Linq.Expressions.Expression]::Call( ...
    +             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
        + FullyQualifiedErrorId : ArgumentNullException   Exception calling "Invoke" with "2" argument(s): "Value cannot be null. Parameter name: body"
    At D:\Test.ps1:146 char:13
    +             $expression2 = $lambdaMethodGeneric2.Invoke($null, @($cal ...
    +             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
        + FullyQualifiedErrorId : ArgumentNullException

PowerShell的下几行是：

foreach ($subsite in $clientContext.web.Webs) {
    Write-Host "Subsite :" $subsite.ServerRelativeUrl
}

我认为嵌套的lambdas可以分为两个ExecuteQuery()，但不确定如何。

在PowerShell中使用嵌套的lambda表达式

0 个答案: