Can a Static Method/Property be saved as a PowerShell Object?-CodePudding

Is it possible to do something like $test = [string]::IsNullOrWhiteSpace and then check whether a $var is Null/Empty/WhiteSpace with $test? I'm not just asking specific to that static method, but in general I've seen folks assign an object to a variable and then take action on the object without typing its full name and I'm wondering if a similar syntax is possible with a string method or any method.

CodePudding user response：

Yes, you can assign .NET methods to variables!

PowerShell returns a PSMethod object when you access a method without a parameter list ( the (...) part after the method name).
This is really just a thin wrapper around the underlying .NET method, and it conveniently allows you to invoke it, using Invoke():

PS ~> $test = [string]::IsNullOrWhiteSpace
PS ~> $test.Invoke("")
True
PS ~> $test.Invoke("   ")
True
PS ~> $test.Invoke("!")
False

CodePudding user response：

To complement Mathias R. Jessen's helpful answer:

If it's acceptable to specify the type every time and only store the method name (or property name) in a variable, you can use normal invocation syntax:

$n = 'IsNullOrWhiteSpace'

[string]::$n('foo') # -> $false
[string]::$n('') # -> $true

The same technique works with instance members:

# Method
$n = 'ToUpper'
'foo'.$n() # -> 'FOO'

# Property
$n = 'Length'
'foo'.$n # -> 3

The above techniques also work with expressions (enclosed in (...)):

# Method
'foo'.('To'   'Upper')() # -> 'FOO'

# Property
'foo'.('Le'   'ngth') # -> 3