Create an array, hashtable and dictionary?

Question

What is the proper way to create an array, hashtable and dictionary?

$array = [System.Collections.ArrayList]@() 

$array.GetType() returns ArrayList, OK.

$hashtable = [System.Collections.Hashtable] 

$hashtable.GetType() returns RuntimeType, Not OK.

$dictionary = ?  

How to create a dictionary using this .NET way?

What is the difference between dictionary and hashtable? I am not sure when I should use one of them.

Answer 1

The proper way (i.e. the PowerShell way) is:

Array:

> $a = @() > $a.gettype()  IsPublic IsSerial Name                                     BaseType -------- -------- ----                                     -------- True     True     Object[]                                 System.Array 

Hashtable / Dictionary:

> $h = @{} > $h.gettype()  IsPublic IsSerial Name                                     BaseType -------- -------- ----                                     -------- True     True     Hashtable                                System.Object 

The above should suffice for most dictionary-like scenarios, but if you did explicitly want the type from Systems.Collections.Generic, you could initialise like:

> $d = New-Object 'system.collections.generic.dictionary[string,string]' > $d.gettype()  IsPublic IsSerial Name                                     BaseType -------- -------- ----                                     -------- True     True     Dictionary`2                             System.Object  > $d["foo"] = "bar" > $d | Format-Table -auto  Key   Value ---   ----- foo   bar 

Answer 2

If you want to initialize an array you can use the following code:

$array = @()    # empty array $array2 = @('one', 'two', 'three')   # array with 3 values 

If you want to initialize hashtable use the following code:

$hashtable = @{}   # empty hashtable $hashtable2 = @{One='one'; Two='two';Three='three'}   # hashtable with 3 values 

Hashtable and dictionary in Powershell is pretty much the same, so I suggest using hashtable in almost all cases (unless you need to do something in .NET where Dictionary is required)