OrderedDictionary key name at specified index

Question

Given an ordered dictionary, I would like to get the key at index 0. I can of course do a loop, get the key of the first iteration and immediately break out of the loop. But I wonder if there is a way to do this directly? My Google-Fu has not turned up anything, and some shots in the dark have failed too. I have tried things like

$hash[0].Name

and

$hash.GetEnumerator()[0].Name

I found this discussion about doing it in C#, which lead to this

[System.Collections.DictionaryEntry]$test.Item(0).Key

but that fails too. Is this just something that can't be done, or am I going down the wrong path?

Answer 1

Use the .Keys collection:

$orderedHash = [ordered] @{ foo = 1; bar = 2 }

# Note the use of @(...)
@($orderedHash.Keys)[0] # -> 'foo'

Note:

• Use of @(...), the array-subexpression operator, enumerates the .Keys collection and collects its elements in an [object[]] array, which enables access by positional indices.

  • The .Keys collection itself implements only the System.Collections.ICollection interface, which supports enumeration, but not indexed access.

  • @(...) to enable indexing will no longer be necessary in PowerShell (Core) 7.3+ (.NET 7+), thanks to an improvement initiated by iRon via GitHub issue #56835: The .Keys collection will then implement the System.Collections.IList interface, which does support positional indexing. Note that this change will only apply to ordered hashtables ([ordered] @{ ... }, System.Collections.Specialized.OrderedDictionary), not also to regular (unordered) hashtables (@{ ... }) or other types implementing the System.Collections.IDictionary interface. However, iRon has created a follow-up proposal to make the .Keys property indexable for all (definition-)ordered and sorted dictionaries - see GitHub issue #63537.

• .Name is an alias property provided by PowerShell; the type-native property containing each System.Collections.DictionaryEntry's key is .Key