c# - 从 cmdlet 中的管道正确获取文件路径

Question

我写了小测试代码:

namespace Test {
  using System;
  using System.Management.Automation;
  using System.Linq;
  using System.IO;

  [Cmdlet(VerbsCommon.Get, "Test", DefaultParameterSetName="Path")]
  public sealed class GetTestCommand : PSCmdlet {
    private String[] _paths;
    private Boolean  _wildcards;

    [Parameter(
      ParameterSetName="Path",
      Mandatory=true,
      Position=0,
      ValueFromPipeline=true,
      ValueFromPipelineByPropertyName=true
    )]
    public String[] Path {
      get { return _paths; }
      set {
        _wildcards = true;
        _paths = value;
      }
    }

    [Parameter(
      ParameterSetName="LiteralPath",
      Mandatory=true,
      Position=0,
      ValueFromPipeline=false,
      ValueFromPipelineByPropertyName=true
    )]
    public String[] LiteralPath {
      get { return _paths; }
      set { _paths = value; }
    }

    protected override void ProcessRecord() {
      ProviderInfo pi;

      (from p in _paths
      select new {
        FilePath = (_wildcards ?
          this.SessionState.Path.GetResolvedProviderPathFromPSPath(p, out pi)[0] :
          this.SessionState.Path.GetUnresolvedProviderPathFromPSPath(p))
      }).ToList()
      .ForEach(i => WriteObject(i.FilePath));
    }
  }
}

这个有效:

Get-Test *.txt

这有效:

Get-ChildItem -Filter *.txt | Get-Test

但这行不通:

Get-ChildItem -Filter *.txt -Recurse | Get-Test

请向我解释哪里出了问题、如何解决以及我应该阅读哪些内容以深入了解 PowerShell 的机制。

Answer 1

问题是您实际上没有处理从 Powershell cmdlet 收到的对象。 正确的做法是将接收到的参数绑定(bind)到适当类型的对象，然后访问其属性，即:

[Cmdlet(VerbsCommon.Get, "Test", DefaultParameterSetName = "Path")]
public sealed class GetTestCommand : PSCmdlet
{
    private FileSystemInfo[] _paths;

    [Parameter(
      ParameterSetName = "Path",
      Mandatory = true,
      Position = 0,
      ValueFromPipeline = true,
      ValueFromPipelineByPropertyName = true
    )]
    public FileSystemInfo[] Path
    {
        get { return _paths; }
        set
        {
            _paths = value;
        }
    }


    protected override void ProcessRecord()
    {
        ProviderInfo pi;

        (from p in _paths
         where (p.GetType() != typeof(DirectoryInfo))
         select new
         {
             FilePath = p.FullName}).ToList()
        .ForEach(i => WriteObject(i.FilePath));
    }
}

为了将来引用，您可能需要使用 Get-ChildItem | 检查从 cmdlet 接收到的类型foreach-object-process { $_.GetType() } . 更重要的是，您实际上可以使用 Powershell 以相同的方式实现您想要的，例如:Get-ChildItem | foreach-object-process { $_.FullName }.

要获得与纯 Powershell 完全相同的结果，请尝试:

Get-ChildItem -Recurse | ForEach-Object -Process { if ($_ -isnot [System.IO.DirectoryInfo]) { Write-Host $_.FullName } }