如何支持作业

项目
09/26/2021

此示例演示如何在编写 cmdlet 时支持作业。如果希望用户将 cmdlet 作为后台作业运行，则必须包括以下过程中所述的代码。有关后台作业的详细信息，请参阅后台作业。

支持作业

定义 AsJob 开关参数，使用户可以决定是否将 cmdlet 作为作业运行。

下面的示例演示了 AsJob 参数声明。
```
[Parameter()]
public SwitchParameter AsJob
{
  get { return asjob; }
  set { asjob = value; }
}
private bool asjob;
```
创建一个派生自 system.object 类的对象。此对象可以是自定义作业对象，也可以是 Windows PowerShell 提供的作业对象之一，如Pseventjob对象。

下面的示例演示一个自定义作业对象。
```
private SampleJob job = new SampleJob("Get-ProcAsJob");
```

在记录处理方法中，添加 if 语句以检测 cmdlet 是否应作为作业运行。下面的代码使用 ProcessRecord 方法来实现。

protected override void ProcessRecord()
{
  if (asjob)
  {
    // Add the job definition to the job repository,
    // return the job object, and then create the thread
    // used to run the job.
    JobRepository.Add(job);
    WriteObject(job);
    ThreadPool.QueueUserWorkItem(WorkItem);
  }
  else
  {
    job.ProcessJob();
    foreach (PSObject p in job.Output)
    {
      WriteObject(p);
    }
  }
}

对于自定义作业对象，请实现 job 类。

private class SampleJob : Job
{
  internal SampleJob(string command)
      : base(command)
  {
    SetJobState(JobState.NotStarted);
  }
  public override string StatusMessage
  {
    get { throw new NotImplementedException(); }
  }

  public override bool HasMoreData
  {
    get
    {
      return hasMoreData;
    }
  }
  private bool hasMoreData = true;

  public override string Location
  {
    get { throw new NotImplementedException(); }
  }

  public override void StopJob()
  {
    throw new NotImplementedException();
  }

  internal void ProcessJob()
  {
    SetJobState(JobState.Running);
    DoProcessLogic();
    SetJobState(JobState.Completed);
  }

  // Retrieve the processes of the local computer.
  void DoProcessLogic()
  {
    Process[] p = Process.GetProcesses();

    foreach (Process pl in p)
    {
      Output.Add(PSObject.AsPSObject(pl));
    }
    Output.Complete();
  } // End DoProcessLogic.
} // End SampleJob class.

如果该 cmdlet 执行工作，请调用 WriteObject 方法，以将进程对象返回到管道。如果以作业的形式执行工作，请将子作业添加到作业。

void DoProcessLogic(bool asJob)
{
  Process[] p = Process.GetProcesses();

  foreach (Process pl in p)
  {
    if (!asjob)
    {
      WriteObject(pl);
    }
    else
    {
      job.ChildJobs[0].Output.Add(PSObject.AsPSObject(pl));
    }
  }
} // End DoProcessLogic.

示例

下面的示例代码演示了一个 cmdlet 的代码 Get-Proc ，该代码可在内部或通过使用后台作业检索进程。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Management.Automation;  // Windows PowerShell namespace.
using System.Threading;              // Thread pool namespace for posting work.
using System.Diagnostics;            // Diagnostics namespace for retrieving
                                     // process objects.

// This sample shows a cmdlet whose work can be done by the cmdlet or by using
// a background job. Background jobs are executed in their own thread,
// independent of the pipeline thread in which the cmdlet is executed.
//
// To load this cmdlet, create a module folder and copy the GetProcessSample06.dll
// assembly into the module folder. Make sure that the path to the module folder
// is added to the $PSModulePath environment variable.
// Module folder path:
//    user/documents/WindowsPowerShell/modules/GetProcessSample06
//
// To import the module, run the following command: Import-Module GetProcessSample06.
// To test the cmdlet, run the following command: Get-Proc -name <process name>
//

//
namespace Microsoft.Samples.PowerShell.Commands
{
  /// <summary>
  ///  This cmdlet retrieves process internally or returns
  ///  a job that retrieves the processes.
  /// </summary>
  [Cmdlet(VerbsCommon.Get, "Proc")]
  public sealed class GetProcCommand : PSCmdlet
  {

    #region Parameters
    /// <summary>
    /// Specify the Name parameter. This parameter accepts
    /// process names from the command line.
    /// </summary>
    [Parameter(
               Position = 0,
               ValueFromPipeline = true,
               ValueFromPipelineByPropertyName = true)]
    [ValidateNotNullOrEmpty]
    public string[] Name
    {
      get { return processNames; }
      set { processNames = value; }
    }
    private string[] processNames;

    /// <summary>
    /// Specify the AsJob parameter. This parameter indicates
    /// whether the cmdlet should retrieve the processes internally
    /// or return a Job object that retrieves the processes.
    /// </summary>
    [Parameter()]
    public SwitchParameter AsJob
    {
      get { return asjob; }
      set { asjob = value; }
    }
    private bool asjob;

    #endregion Parameters

    #region Cmdlet Overrides

    // Create a custom job object.
    private SampleJob job = new SampleJob("Get-ProcAsJob");

    /// <summary>
    /// Determines if the processes should be retrieved
    /// internally or if a Job object should be returned.
    /// </summary>
    protected override void ProcessRecord()
    {
      if (asjob)
      {
        // Add the job definition to the job repository,
        // return the job object, and then create the thread
        // used to run the job.
        JobRepository.Add(job);
        WriteObject(job);
        ThreadPool.QueueUserWorkItem(WorkItem);
      }
      else
      {
        job.ProcessJob();
        foreach (PSObject p in job.Output)
        {
          WriteObject(p);
        }
      }
    }
    #endregion Overrides

    // Implement a custom job that derives
    // from the System.Management.Automation.Job class.
    private class SampleJob : Job
    {
      internal SampleJob(string command)
          : base(command)
      {
        SetJobState(JobState.NotStarted);
      }
      public override string StatusMessage
      {
        get { throw new NotImplementedException(); }
      }

      public override bool HasMoreData
      {
        get
        {
          return hasMoreData;
        }
      }
      private bool hasMoreData = true;

      public override string Location
      {
        get { throw new NotImplementedException(); }
      }

      public override void StopJob()
      {
        throw new NotImplementedException();
      }

      internal void ProcessJob()
      {
        SetJobState(JobState.Running);
        DoProcessLogic();
        SetJobState(JobState.Completed);
      }

      // Retrieve the processes of the local computer.
      void DoProcessLogic()
      {
        Process[] p = Process.GetProcesses();

        foreach (Process pl in p)
        {
          Output.Add(PSObject.AsPSObject(pl));
        }
        Output.Complete();
      } // End DoProcessLogic.
    } // End SampleJob class.

    void WorkItem(object dummy)
    {
       job.ProcessJob();
    }

    // Display the results of the work. If not a job,
    // process objects are returned. If a job, the
    // output is added to the job as a child job.
    void DoProcessLogic(bool asJob)
    {
      Process[] p = Process.GetProcesses();

      foreach (Process pl in p)
      {
        if (!asjob)
        {
          WriteObject(pl);
        }
        else
        {
          job.ChildJobs[0].Output.Add(PSObject.AsPSObject(pl));
        }
      }
    } // End DoProcessLogic.
  } //End GetProcCommand
}

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如何支持作业

支持作业

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