Hashtable vs array of custom objects regarding iteration

Question

I frequently write lists of things and perform enumeration against them to perform some get/set.

I hate enumerating hashtables, since whenever I have to do it, I have to bend my mind backwards to work with hashtable objects.

$hashtablelistofitems = @{}

$hashtablelistofitems.add("i'm a key", "i'm a value")

foreach ($item in $hashtablelistofitems.keys) {
  $item
  $hashtablelistofitems.item($item)
}

Instead, I usually revert to using a single dimensional array of a custom object with two noteproperties.

$array = @()

$listofitems = "" | select key,value

$listofitems.key = "i'm a key"
$listofitems.value = "i'm a value"

$array += $listofitems

foreach ($item in $listofitems) {
  $item.key
  $item.value
}

Why should I be using a hashtable over this method? Simply because it only guarantees a single value per key?

Answer 1

You should use a hashtable if you want to store a key value list and not create an array containing a custom object with two properties (key / values) for mainly two reasons:

1. You might want to pass your hashtable to a function that expect a hashtable.
2. Hashtable is a built-in PowerShell type which users are aware of. Your second approach is harder to read / maintain for other users.

Note: You can iterate over a hashtable almost the same way as your approach by calling the GetEnumerator() function:

foreach ($item in $listofitems.GetEnumerator()) {
  $item.key
  $item.value
}

---

Also, the hashtable comes with handy methods that you might want to use:

@{} | Get-Member | Where-Object MemberType -eq Method | Select Name

Output:

Name             
----             
Add              
Clear            
Clone            
Contains         
ContainsKey      
ContainsValue    
CopyTo           
Equals           
GetEnumerator    
GetHashCode      
GetObjectData    
GetType          
OnDeserialization
Remove           
ToString  

Answer 2

This is nowhere near as useful as Martin's compendium, but it's useful enough.

It's an MSDN article about how to convert back and forth between Hashtables and PSCustomObjects. The article