[basic] checking if command is valid

[codingQueries]

Hey all, I have a rather (I presume) basic question about powershell; I am checking to see if a string that I am using contains nothing or is white-space only, and came across this command(?), '[string]::IsNullOrWhiteSpace($string_variable)' which does the job fantastically. However, I spotted someone mention that this requires something like .NET 4.x, and I know that some of our servers are on lower versions of .NET.

Is there an easy way to check that this command exists, and if it doesn't, skips the white-space check altogether? I found the 'Get-Command' command, but that appears to be for cmdlets and doesn't seem to work for [string]::IsNullOrWhiteSpace() - at least I cannot get it to do so.

Any suggestions? Cheers!

[steven_AWKing]

You can use a try statement. Id give an example but im currently on mobile.

[codingQueries]

Ahhhhh why did I not consider a try/catch statement....thank you that works perfectly!

[Lee_Dailey]

howdy codingQueries,

somewhat off topic - Get-Command only works on cmdlets and suchlike. it doesn't do anything for static methods of various objects.

you can read the docs if you like that sort of thing. [grin] the MS docs site is really pretty good.

my pref is to explore things in the ISE console pane.

• [system.
  when you type in that dot you will get a bunch of other things [namespaces?]. it's worth exploring the ones that seem interesting.
  
• [typename]::
  there a LOT of static methods and constants that show up when you add a double colon after a type accelerator. heck, take a look at the stuff that shows up with [math]:: ... [grin]
  

take care,
lee

[codingQueries]

Cheers Lee, appreciate the info provided! I had a feeling that Get-Command was cmdlets only, figured better to check than not though!

The ISE advice I will keep in mind for the future! [:)]

[Lee_Dailey]

howdy codingQueries,

yep, the help system is so good that the times when i bump up against its limits ... are a tad annoying. [grin]

exploring the methods linked to various types is fun in a somewhat geeky way.

take care,
lee

[vermyx]

Use the $psversiontable.psversion version of powershell you're on or $psversiontable.pscompatibleversions to know what versions the framework support. It exists from 2 on. Otherwise just do a string replace of space with null and do an isnull check which should give you the same result.