PowerShell: $null and parameter type

4 Comments

• Any idea on how to stop it from doing that?
  
  It appears that Powershell does this cast even when calling into an assembly (such as the SharePoint API), and null != String.Empty.
  

• I have the same problem calling tfs method QueryLabels.
  
  This code in Powershell
  
  $labels = $vcs.QueryLabels("REL_1_*","$/ProjectX",$null,$false)
  
  is not hte same as this in C#
  
  VersionControlLabel[] labels = vcs.QueryLabels("REL_1_*", "$/ProjectX", null, false);
  

• The only workaround I have been able to find for calling .Net assemblies is to write a cmdlet to wrap your call to .net assembly. This works fine.
  
  WriteObject(Vcs.QueryLabels(label, Scope, User, IncludeItems));
  
  Full Code below:
  using System;
  using System.Collections.Generic;
  using System.Text;
  using System.Management.Automation;
  using System.Collections;
  using Microsoft.TeamFoundation.VersionControl.Client;
  
  namespace WindowsPowerShell1
  {
  [Cmdlet(VerbsCommon.Get, "Label", SupportsShouldProcess = true)]
  public class GetLabel : Cmdlet
  {
  private string label;
  private string scope;
  private VersionControlServer vcs;
  private string user;
  private bool includeItems;
  
  #region Parameters
  [Parameter(Position = 0,
  Mandatory = true,
  ValueFromPipelineByPropertyName = true,
  HelpMessage="The label name - * is wildcard")]
  [ValidateNotNullOrEmpty]
  public string Label
  {
  get { return label; }
  set { label = value; }
  }
  [Parameter(Position = 1,
  Mandatory = true,
  ValueFromPipelineByPropertyName = true,
  HelpMessage = "Scope")]
  [ValidateNotNullOrEmpty]
  public string Scope
  {
  get { return scope; }
  set { scope = value; }
  }
  [Parameter(Position = 2,
  Mandatory = true,
  ValueFromPipelineByPropertyName = true,
  HelpMessage = "VersionControlServer")]
  [ValidateNotNull]
  public VersionControlServer Vcs
  {
  get { return vcs; }
  set { vcs = value; }
  }
  [Parameter(Position = 3,
  Mandatory = false,
  ValueFromPipelineByPropertyName = true,
  HelpMessage = "VersionControlServer")]
  public string User
  {
  get { return user; }
  set { user = value; }
  }
  [Parameter(Position = 4,
  Mandatory = true,
  ValueFromPipelineByPropertyName = true,
  HelpMessage = "IncludeItems")]
  public bool IncludeItems
  {
  get { return includeItems; }
  set { includeItems = value; }
  }
  #endregion
  
  protected override void ProcessRecord()
  {
  try
  {
  WriteObject(Vcs.QueryLabels(label, Scope, User, IncludeItems));
  }
  catch (Exception)
  {
  }
  }
  }
  }
  

• Wow! I could not even guess about it)) Not bad.