HashTable

HashTable is essentially System.Collections.HashTable, the non-generic version of Dictionary<,>.

@{} -is [System.Collections.IDictionary] # True
@{} -is [System.Collections.HashTable] # True

TIP

HashTable serves as more like a dictionary with syntax sugar, if you want it to be more like object literal, use [pscustomobject].

Creation

PowerShell has builtin syntax for creating a HashTable. Inline declaration requires ; to distinguish key-value pairs.

$foo = @{
    Name = 'foo'
    Age = 18
}

$foo = @{ Name = 'foo'; Age = 18 }

Ordered HashTable

[ordered] is a mark can be used when creating HashTable literal, it makes sure that all entries are ordered as in declaration and subsequent appending.

([ordered]@{
    C = 'C'
    B = 'B'
    A = 'A'
}).Keys # C B A #

@{
    C = 'C'
    B = 'B'
    A = 'A'
}.Keys # B C A #

NOTE

[ordered] can not be used as type, but it's indeed a System.Collections.Specialized.OrderedDictionary.

([ordered]@{}).GetType().FullName # System.Collections.Specialized.OrderedDictionary

Access Values

You can access value of one or more keys by indexer.

$foo['Name'] # foo
$foo['Name', 'Age'] # @('foo', 18)

NOTE

PowerShell uses TryGetValue when accessing value with indexer syntax for IDictionary types, so it never throw.

. accessor would also works as long as there's no duplicated Extended Property with the same name of the key you passed.

$foo.Name # foo
$foo.'Name'
$name = 'name'
$foo.$name

TIP

Always use indexer to access value of a HashTable. . will prefer Extended Property that might be unexpected.

NOTE

Key in HashTable can be any type. So if the key is not a singular type, you'll have to extract the key from Keys first and then access the value by the key.

Merging

@{ foo = 123; bar = '123' } + @{ baz = 234 }

WARNING

+ will throw if the two have any duplicated key.