.net - Primitive values of WMI classes -


this complicated idea, , hope you'll bear me articulation difficult.

it seems wmi classes have primitive value can queried, while others not. has practical significance.

demo 1

take, instance, win32_processor class. primitive value, far can tell, value of instance's deviceid column. allows querying, example, architecture (32 / 64-bitness) of running os tidy one-liner, jscript example:

var arch = getobject("winmgmts:root\\cimv2:win32_processor='cpu0'").addresswidth

in example, getobject acts sort of select instance primitive value="cpu0" , returns single instance, rather collection. works intended.

demo 2

on other hand, win32_operatingsystem class has no primitive value i've been able find. win32_processor class deviceid column, msdn documentation win32_operatingsystem claims creationclassname column table's key field.

assume predictably, creationclassname=="win32_operatingsystem". therefore, 1 might infer similar one-liner written thusly:

var arch = getobject("winmgmts:root\\cimv2:win32_operatingsystem='win32_operatingsystem'").osarchitecture

however, results in error. trial-and-error attempts @ using other column values have equally met failure. appending .columname between classname , = results in syntax error well.

as far can tell, there's no way identify single instance of win32_operatingsystem class without enumerating instances, if there 1 instance enumerate.

var wmi = getobject("winmgmts:"); var os = wmi.execquery("select osarchitecture win32_operatingsystem"); (var res = new enumerator(os); !res.atend(); res.movenext()) {     var arch = res.item().osarchitecture; }

these lines can combined somewhat:

var os = getobject("winmgmts:").execquery("select osarchitecture win32_operatingsystem"); var arch = new enumerator(os).item().osarchitecture;

... it'd still nice query instance directly within win32_operatingsystem without having enumerate irritatingly vestigial hierarchy.

the question

how can predict whether wmi class has primitive value can queried, , column contains value?

what you're looking 'key' property.

http://blogs.msdn.com/b/powershell/archive/2008/04/15/wmi-object-identifiers-and-keys.aspx


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