{"id":6361,"date":"2008-04-15T09:30:00","date_gmt":"2008-04-15T09:30:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/powershell\/2008\/04\/15\/wmi-object-identifiers-and-keys\/"},"modified":"2019-02-18T13:16:02","modified_gmt":"2019-02-18T20:16:02","slug":"wmi-object-identifiers-and-keys","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/powershell\/wmi-object-identifiers-and-keys\/","title":{"rendered":"WMI Object Identifiers and Keys"},"content":{"rendered":"

Recently one of MVPs, Darren Mar-Elia<\/a> (Group Policy Guru from SDMSoftware<\/a> [which as a set of FREE PowerShell GP cmdlets HERE<\/a>])  was working with our WMI type accelerators and got the following error:<\/p>\n

$ld = ‘\\\\sdmlaptop1\\root\\cimv2:Win32_LogicalDisk.Caption=”C:”‘<\/font><\/p>\n

$disk = [WMI] $ld<\/font><\/p>\n

Cannot convert value “<\/font>\\\\sdmlaptop1\\root\\cimv2:Win32_LogicalDisk.Caption=<\/font><\/a>“C:”” to type “System.Management.ManagementObject”. Error: “Invalid object path “<\/font><\/p>\n

At line:1 char:17<\/font><\/p>\n

+ $disk = [WMI] $ld <<<<<\/font><\/p>\n

This is a great opportunity to discuss WMI Key properties<\/strong>.  WMI is an awesome piece of infrastructure.  It has a rich object metamodel which includes metadata on properties.  What does that mean?  Think of it as Reflection+++.   It means that you can ask WMI a rich set of questions about the object\/type you have.  In this example, you can ask WMI which of the properties of a class can be used as a KEY, in other words as an object identifier.  <\/p>\n

[NOTE<\/strong>: These demos are all using the V2 CTP syntax.  If you want to do the same thing on V1, just put the term “psbase.” in front of “properties” .  e.g. instead of $c.Properties  you’ll type $c.psbase.Properties – jps]<\/p>\n

PS>$c=[wmiclass]”win32_logicaldisk”
PS>$c.Properties[“caption”] <\/font><\/p>\n

Name       : caption
Value      :
Type       : String
IsLocal    : False
IsArray    : False
Origin     : CIM_ManagedSystemElement
Qualifiers : {CIMTYPE, MaxLen, read} <\/font><\/p>\n

PS>$c.Properties[“deviceid”] <\/font><\/p>\n

Name       : deviceid
Value      :
Type       : String
IsLocal    : False
IsArray    : False
Origin     : CIM_LogicalDevice
Qualifiers : {CIM_Key, CIMTYPE, key<\/font><\/strong>, MappingStrings…}<\/font><\/p>\n

Here is a function I wrote to make this a little easier:<\/p>\n

function Get-WmiKey
{
  $class = [wmiclass]$args[0]
  $class.Properties |
      Select @{Name=”PName”;Expression={$_.name}} -Expand Qualifiers |
      Where {$_.Name -eq “key”} |
      foreach {$_.Pname}
}<\/p>\n

PS>Get-WmiKey Win32_LogicalDisk
DeviceID
PS>Get-WmiKey Win32_Process
Handle
PS>Get-WmiKey Win32_Service
Name
PS><\/p>\n

So if we believe what this is telling us, it means that the Darren’s original string should have used the “DeviceID” property instead of the “Caption”.  Let’s see if that works.<\/p>\n

PS>$ld = ‘\\\\jpslap11\\root\\cimv2:Win32_LogicalDisk.Caption=”C:”‘
PS>[wmi]$ld
Cannot convert value “\\\\jpslap11\\root\\cimv2:Win32_LogicalDisk.Caption=”C:”” to type “System.Management.ManagementObject
“. Error: “Invalid object path ”
At line:1 char:9
+ [wmi]$ld <<<<
<\/font>PS>$ld = ‘\\\\jpslap11\\root\\cimv2:Win32_LogicalDisk.DeviceID=”C:”‘
PS>[wmi]$ld <\/font><\/p>\n

DeviceID     : C:
DriveType    : 3
ProviderName :
FreeSpace    : 18366902272
Size         : 85446352896
VolumeName   : PowerShell Rocks!<\/font><\/p>\n

As I mentioned, WMI is an awesome technology.  Key properties are just the beginning of it.  Check out the other WMI property qualifiers HERE<\/a> and start experimenting!<\/p>\n

In closing let me say that throughout the history of PowerShell, a small subset of people have looked at it and said, “WMI is dead”.  I must tell you that I’ve never understood what they were talking about.  I LOVE WMI.  PowerShell is a direct outgrowth of the work I did on the WMI command line.  If you’ve played with our CTP release, you’ll see that we are investing very heavily in supporting WMI and making WMI a REALLY GOOD CHOICE for surfacing your management information (you’ll see that even more in the next drop of the CTP [ what you’ll be able to do with WMI will BLOW YOUR SOCKS OFF – and we’ll be doing even more!]).<\/p>\n

Cheers!<\/p>\n

Jeffrey Snover [MSFT]
Windows Management Partner Architect
Visit the Windows PowerShell Team blog at:    http:\/\/blogs.msdn.com\/PowerShell<\/a>
Visit the Windows PowerShell ScriptCenter at:  http:\/\/www.microsoft.com\/technet\/scriptcenter\/hubs\/msh.mspx<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Recently one of MVPs, Darren Mar-Elia (Group Policy Guru from SDMSoftware [which as a set of FREE PowerShell GP cmdlets HERE])  was working with our WMI type accelerators and got the following error: $ld = ‘\\\\sdmlaptop1\\root\\cimv2:Win32_LogicalDisk.Caption=”C:”‘ $disk = [WMI] $ld Cannot convert value “\\\\sdmlaptop1\\root\\cimv2:Win32_LogicalDisk.Caption=“C:”” to type “System.Management.ManagementObject”. Error: “Invalid object path “ At line:1 char:17 […]<\/p>\n","protected":false},"author":600,"featured_media":13641,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[26],"class_list":["post-6361","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-powershell","tag-wmi"],"acf":[],"blog_post_summary":"

Recently one of MVPs, Darren Mar-Elia (Group Policy Guru from SDMSoftware [which as a set of FREE PowerShell GP cmdlets HERE])  was working with our WMI type accelerators and got the following error: $ld = ‘\\\\sdmlaptop1\\root\\cimv2:Win32_LogicalDisk.Caption=”C:”‘ $disk = [WMI] $ld Cannot convert value “\\\\sdmlaptop1\\root\\cimv2:Win32_LogicalDisk.Caption=“C:”” to type “System.Management.ManagementObject”. Error: “Invalid object path “ At line:1 char:17 […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/posts\/6361","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/users\/600"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/comments?post=6361"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/posts\/6361\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/media\/13641"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/media?parent=6361"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/categories?post=6361"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/tags?post=6361"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}