So the question is fairly simple but I'm not sure how to word it in order to find the answer.
I'm trying to access a class i.e. [MyCustomClass] in order to check static properties but I need to do it dynamically. How do I inject the class name like [$className]?
Or are there any cmdlets or .NET class functions I can use for this purpose? I tried searching Get-Command *Class* and some similar commands but am not coming up with anything.
There are 2 primary options for resolving a given type by name, each with slightly different behavior:
[type]:$className = 'MyCustomClass'
$myType = [type]$className
Attempting to cast a non-existing type name will throw an exception:
PS ~> [type]'Not actually a type'
Cannot convert the "Not actually a type" value of type "System.String" to type "System.Type".
At line:1 char:1
+ [type]'Not actually a type'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidArgument: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvalidCastFromStringToType
-as type conversion operator (introduced in PowerShell version 3.0):$myType = 'MyCustomClass' -as [type]
Unlike casting, the -as operator never throws - it simply returns $null:
PS ~> $myType = 'this does not exist' -as [type]
PS ~> $null -eq $myType
True
Common for both of these is that you can now resolve the static members of [MyCucstomClass]:
$myType::MyProperty
The static member operator :: also works on instance references, so if you have an object of type [MyCustomClass], use that in place of a type literal:
class MyClass
{
static [string] $StaticValue = 'Static string value'
}
PS ~> $instance = [MyClass]::new()
PS ~> $instance::StaticValue
Static string value
You can use Invoke-Expression to run something you still have to build:
$class = 'DateTime'
Invoke-Expression "[$class]::Now"
Invoke-Expression (iex) should generally be avoided and used only as a last resort, due to its inherent security risks. In short: Avoid it, if possible, given that superior alternatives are usually available. If there truly is no alternative, only ever use it on input you either provided yourself or fully trust - see this answer.Invoke-Expression :-)