Credit: Mark Kraus
Website: https://get-powershellblog.blogspot.com
- Use Arrays if you know the element types and have a fixed length and/or known-up-front collection size that will not change.
- Use ArrayList if you have an unkown collection size with either unknown or mixed type elements.
- Use a Generic List when know the type of the elements but not the size of the collection.
- Use a HashTable if you are going to do key based lookups on a collection and don't know the object type of the elements.
- Use a Dictionary<TKey, TValue> you are going to do key based lookups on a collection and you know the type of the elements.
- Use a HashSet when you know the type of elements and just want unique values and quick lookups and assignmnets.
- Use LinkList if you are going to make large numbers of additions and subtractions to an ordered list (and have the understanding to use this type)
- Use Queue if you will build a collection that will need to be worked on First-in-first-out FIFO
- Use Stack if you will build a collection that will need to be worked Last-in-first-out LIFO
- Use SortedSet when you need a HasSet like set, but sorted (alaphbetically, for example)
- Use SortedList when you need a List, but sorted (alaphbetically, for example)
- Use SortedDictionary<TKey, TValue> when you need a Dictionary<TKey, TValue>, but sorted (alaphbetically, for example)
- Do not use Object[]
- Do not use += on Arrays. If your collection will grow or shrink, use ArrayList or List
- Do not use List for value types (int32, int64, char, etc)
- avoid using Arrays, Lists, and ArrayLists for lookup/search operations, use ditcionaries and sets instead
- Linked lists should only be considered in rediculously high volume add/remove operations to a list as the code complexity is too much for PowerShell
- Only use "sorted" types when you really need to. If you only need it for reconstituion, sorting the keys and then foreaching them can work on small collections
https://docs.microsoft.com/en-us/dotnet/api/system.array?view=netframework-4.7.1 string array:
$Array = [string[]]@('string1','string2')
Int array:
$Array = [int[]]@(1,2,3,4,5)
https://docs.microsoft.com/en-us/dotnet/api/system.collections.arraylist?view=netframework-4.7.1
$ArrayList = [System.Collections.ArrayList]::new()
$null = $ArrayList.Add(1)
$null = $ArrayList.Add('String1')
$List = [System.Collections.Generic.List[String]]::new()
$List.Add('String1')
$List.Add('String2')
Int:
$List = [System.Collections.Generic.List[Int]]::new()
$List.Add(1)
$List.Add(2)
https://docs.microsoft.com/en-us/dotnet/api/system.collections.hashtable?view=netframework-4.7.1
$HashTable = @{
Key1 = "Value1"
Key2 = "Value2"
}
https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2?view=netframework-4.7.1 Case Sensitive (default)
$Dictionary = [System.Collections.Generic.Dictionary[String,String]]::New()
$Dictionary['key1'] = 'Value1'
$Dictionary['key2'] = 'Value2'
# Is case sensitiveby default:
$Dictionary['Key2'] = 'Value3'
Case Insensitive:
$Comparer = [System.StringComparer]::InvariantCultureIgnoreCase
$Dictionary = [System.Collections.Generic.Dictionary[String,String]]::New($Comparer)
$Dictionary['key1'] = 'Value1'
$Dictionary['key2'] = 'Value2'
# Will repllace the key above
$Dictionary['Key2'] = 'Value3'
Example using processes and looking them up by PID:
$ProcessDict = [System.Collections.Generic.Dictionary[int,System.Diagnostics.Process]]::new()
Get-Process | ForEach-Object {
$ProcessDict[$_.Id] = $_
}
$ProcessDict[0] | format-list *
In c# sortlist this fifo or lifo?