$string.IndexOf('.') inside powershell function returns method invocation failed

Question

Function doSomething($param1 $param2 $file)
{
...doing stuff
$pos = $file.IndexOf('.')
}

doSomething -param1 'stuff' -param2 'more stuff' -file 'C:\test.txt'

Returns error: Method invocation failed because [System.IO.FileInfo] doesn't contain a method named 'IndexOf'.

But calling it outside a function or from the command line works with out issue.

Is this a limitation of powershell or is there some trick to calling string functions inside powershell functions?

Thanks for the help!

Anthony Neace · Accepted Answer · 2013-09-25 01:10:20Z

12

IndexOf is a method of type string. I suspect that somewhere in ...doing stuff, you're operating on $file in such a way that it becomes treated as a System.IO.FileInfo.

I suspect this in part because I've tried to replicate it in my environment and got it to work:

function doSomething ($file) 
{ 
    # This gets the index of . in 'C:\test.txt', which should be at position 7.
    $pos = $file.IndexOf('.')
    $pos
    $file.GetType() 
}
doSomething -file 'C:\test.txt'
7

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     String                                   System.Object

Are you operating on $file at all, or using it to modify other files? If you are and don't mind the object being a [System.IO.FileInfo], you can use $file.fullname to get your path string back. This assumes that you haven't modified it in such a way that it has become a collection of FileInfo objects.

answered Sep 25, 2013 at 1:10

Anthony Neace

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1 Comment

Dane Boulton Over a year ago

You were correct I was creating file a System.IO.FileInfo object. I was generating $file with get-childitem for a folder path. It doesnt need to stay as a System.IO.FileInfo object for what I need so I just converted it to a string $file.tostring() and I am able to use indexOf. Thanks for the help!!

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