2

I know I can add to an [Ordered] hash table at a particular index, with

$ordered.Insert([Int], [String], [String])

and I can set the value at a certain index with

$ordered[[Int]] =

And that leads me to THINK that I should also be able to GET the index of a given key. It seems that direct access isn't possible, as there in no .IndexOf() method. But I know I can get an array of the keys, and an array does have .IndexOf(), but that then returns another array, of -1 for the non matches and 0 for the matches. So

$ordered = [Ordered]@{
    'one' = 1
    'two' = 2
    'three' = 3
    'four' = 4
}
$ordered
$ordered.Keys.IndexOf('two')

produces

Name                           Value                                                                                                                                                                                                                        
----                           -----                                                                                                                                                                                                                        
one                            1                                                                                                                                                                                                                            
two                            2                                                                                                                                                                                                                            
three                          3                                                                                                                                                                                                                            
four                           4                                                                                                                                                                                                                            
-1
0
-1
-1

So now I need to get the index of that 0. So that doesn't seem to be the way to do it. I also found this. And indeed this works.

[Array]::IndexOf($ordered.Keys,'three')

But it has me wondering, is there a way to make the previous approach work? $ordered.Keys.IndexOf([String]) just seems like it should be viable, and I am just missing how to extract only the successful match. But perhaps not, and the static method is the way to go?

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5
  • 2
    In PowerShell Core / .NET Core, OrderedDictionaryKeyValueCollection implements IList so, $ordered[$ordered.Keys.IndexOf('two')] works perfectly fine. In .NET Framework a bit more work is needed tho, I'm surprised you have a real use case for this. Why not explain what you're trying to accomplish as there is likely a better way to do it Commented Oct 1, 2022 at 19:44
  • 1
    It's a pretty edge case situation for sure. Related to my post earlier. I have an ordered hashtable of registry Uninstall keys, and some of those keys are actually extraneous Autodesk junk. Sometimes a redundant GUID key, sometimes a non GUID key, in both cases containing useless Uninstall info. So, I want to find the index of the correct item, and move (delete/add actually) the redundant key so it shows up in the log immediately after the correct one. As an aid in validating the results. It's... ugly. And FWIW, I am limited to PS 5.1. Commented Oct 1, 2022 at 20:00
  • Right I understand but, what is different doing (assuming this was possible for you in pwsh 5.1) $ordered[$ordered.Keys.IndexOf('two')] than doing just this $ordered['two'] or $ordered.ContainsKey('two') for validation ? Maybe If you can add a reproducible example of your problem we may be able to help you find the best solution to the problem, I know what you have right now is a reproducible example but I think the solution you're looking for is reinventing the wheel in this case Commented Oct 1, 2022 at 20:03
  • The key is I need to find the index of 'two' so I can insert something at that index +1. For example, the correct Uninstall data for Autodesk Civil 3D 2023 is found in the {AD211D5C-0BFF-3956-8998-C5C1F8FB5884} key and some rubbish data is found in {28B89EEF-6100-0409-2102-CF3F3A09B77D}. In my log I want the correct log info + X64 {AD211D5C-0BFF-3956-8998-C5C1F8FB5884}: Autodesk Civil 3D 2023 - English (13.5.211.0) [ADSK GUID ODIS (ADSK GUID NULL)] to be immediately followed by the bogus log item, despite the fact that it was actually processed first. Commented Oct 1, 2022 at 20:10
  • And I should say, the bogus item could be a GUID from earlier, or a GUID from later, or a non GUID key from later. Autodesk is ALL OVER the map as far as where info goes. So I process the keys in order, with conditionals that define the valid key and any key to skip, and if the skip has already been processed I can flag it, but if not I add the log item under its own path as the key, while also including the correct path. Then, when I later run across the path to skip, I can extract the correct path, find the index of the correct path, and insert the skip message right after. Fun. :) Commented Oct 1, 2022 at 20:17

2 Answers 2

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2

In Windows PowerShell, use @(...) to convert the .Keys collection to a regular array, on which you can call .IndexOf():

@($ordered.Keys).IndexOf('two')

Note: Unlike direct, key-based access to your ordered hashtable, .IndexOf() is case-sensitive.

As Santiago Squarzon points out, the use of @(...) is no longer necessary in PowerShell (Core) 7.3+ (.NET 7+), where the collection type contained in the .Keys property value itself implements the IList interface and therefore directly supports .IndexOf().

Note:

  • The above also applies to accessing .Keys by index, e.g. @($ordered.Keys)[0] / $ordered.Keys[0]

  • As of this writing, the 7.3+ / .NET 7+ improvement will only apply to System.Collections.Specialized.OrderedDictionary, the type that PowerShell's [ordered] @{ ... } literal syntax creates instances of, and not also to other ordered or sorted dictionary types; GitHub issue #63537 aims to change that.

As for what happened in your attempt:

Since in Windows PowerShell the .Keys collection itself has no .IndexOf() method, member-access enumeration was performed, resulting in .IndexOf() calls - as a string method - on each key.

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5 Comments

good lord, by now I should be used to coercing things to proper arrays. It never occurred to me to check the type of the keys collection. I just assumed it was an array. Doh!
@Gordon, fortunately this isn't a concern anymore in PS Core. As for what happened without @(...) in WinPS: since the .Keys collection itself has no .IndexOf() method, member-access enumeration was performed, resulting in .IndexOf() call - as a string method - on each key.
Yeah, someday I will remember that PowerShell will coerce things when I don't expect it, and have methods with the same name but totally different behavior. I am trying to refactor to use classes, which will help. But I need to be better at looking at what type I am working with as soon as I have problems.
What worries me though is that I want to work in VS Code on Mac, because, well, Windows sucks. And VS Code performance on a Parallels VM also kinda sucks. But that means I will be developing in PS Core but production code runs in PS Windows. I need to make sure I can force VS Code to actually run everything in the PS 5.1 engine so that I don't get caught out by a whole new host of issues. :)
That sounds challenging, @Gordon. You'd have to find a linter that checks PowerShell code for 5.1 compatibility, and I'd be surprised if one existed.
1

As an alternative to mklement0's helpful answer you could also extend the type itself adding a new PSScriptMethod to find index of a Key. This can be accomplished with Update-TypeData.

Update-TypeData -MemberType ScriptMethod -MemberName GetIndexOf -Value {
    param([object] $Key)

    return [array]::IndexOf($this.Keys, $Key)
} -TypeName System.Collections.Specialized.OrderedDictionary

$ordered.GetIndexOf('four') # => 3
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1 Comment

I might not go this route for this particular issues, but good to know this is an option.

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