PowerShell object representation

Question

There are different ways to represent (display) an object in PowerShell but when it comes to complex objects it is either very verbose or quiet useless:

$Object = @{ 'a' = 1; 'b' = 2 }

Just outputting (Format-Host, or Format-List) returns a multiline output, as:

$Object

Name                           Value
----                           -----
a                              1
b                              2

Converting it to a string "$Object" or $Object.ToString() doesn't reveal anything about its contents:

System.Collections.Hashtable

Converting it to Json $Object |ConvertTo-Json -Compress, gets close to what I would like to see (but a little too expressive cmdlet for what I need):

{"a":1,"b":2}

I wonder whether there is a way access the representation formatting used by PowerShell display cmdlets, as e.g. the value behind the ImmediateBaseObject and BaseObject:

$Object.PSObject

Members             : {System.Object Item(System.Object key) {get;set;}, bool IsReadOnly {get;}, bool IsFixedSize {get;}, bool IsSynchronized {get;}…}
Properties          : {bool IsReadOnly {get;}, bool IsFixedSize {get;}, bool IsSynchronized {get;}, System.Collections.ICollection Keys {get;}…}
Methods             : {Add, Clear, Clone, Contains…}
ImmediateBaseObject : {[a, 1], [b, 2]}                     # <-- This representation
BaseObject          : {[a, 1], [b, 2]}                     #
TypeNames           : {System.Collections.Hashtable, System.Object}

Wishful thinking, I would like to be able to do something like this:

[PowerShellFormat]$Object

And get the same formatting back for any (complex) object as shown behind BaseObject for $Object.PSObject.
As for this case:

{[a, 1], [b, 2]}

Answer 1

JosefZ has provided the crucial pointer:

• Call .GetEnumerator() on your dictionary in order to enumerate its entries, which are key-value pairs, such as of type [System.Collections.DictionaryEntry] in hashtable instances.

• Unlike dictionaries as a whole, their entries stringify meaningfully, in the form [<key>, <value>] - though it's important to note that this is just a for-display representation, not suitable for programmatic processing.

• When PowerShell's formatting system stringifies a dictionary stored in a property of an input object, it treats it as an array of entries, and stringifies that array similarly to how arrays are stringified in expandable strings:

  • The difference is that the whole representation is enclosed in {...} and that the (stringified) elements are separated with , . You saw this in the display formatting of @{ 'a' = 1; 'b' = 2 }.psobject (.ImmediateBaseObject and .BaseObject properties).

  • I'm not aware of a public method that would produce this format, but it isn't hard to produce it yourself:

# -> '{[a, 1], [b, 2]}'
'{' + (@( @{ 'a' = 1; 'b' = 2 }.GetEnumerator() ) -join ', ') + '}'

Note:

• The .GetEnumerator() call must be wrapped in @(...) to force actual enumeration, resulting in an array.

• It follows that you can use the above for arrays as inputs too.

---

Getting an analogous string representation or [pscustomobject] instances is much simpler: Use string interpolation, i.e. embed the object in an expandable (double-quoted) string ("..."):

$obj = [pscustomobject] @{ 'a' = 1; 'b' = 2 }
"$obj" # -> '@{a=1; b=2}'

Note:

• Unlike hashtables/dictionaries, [pscsutomobject] instances stringify the same way in expandable strings and as properties of formatted object representations.

• Note the difference in formats compared to the hashtable visualization, with the property name-value pairs separate with = (and no whitespace), multiple properties separated with ;, and @{ as the opening delimiter.
  Curiously, this format is very similar to the syntax of a hashtable literal.

---

Finally, just to demonstrate that PowerShell's formatting system indeed produces the representations above for hashtables and [pscustomobject] instances used as properties:

@{ 
  hashtable = @{ 'a' = 1; 'b' = 2 }
  pscustomobject = [pscustomobject] @{ 'a' = 1; 'b' = 2 }
}

Output:

Name                           Value
----                           -----
pscustomobject                 @{a=1; b=2}
hashtable                      {[a, 1], [b, 2]}

Answer 2

Try this:

$object = @{'a'=1; 'b'=2}
$x = [pscustomobject]$object

'Members'
$x | gm
'  '
'Content'
$x
'  '
'Properties'
$x.a
$x.b
'   '
'CSV format'
$x | ConvertTo-csv
'   '
'Json format'
$x | ConvertTo-Json

This will convert a and b into Noteproperty names, with the corresponding values.