Windows PowerShell 3.0 Hash Tables

PowerShell 3.0 [Ordered] Hash Table

What’s new with hash tables in PowerShell 3.0 is they can be[Ordered].  With just one command you can sequence values thus: [Ordered]@{"Key1" = "Value 1";"Key2" = "Value 2; etc …"}.


Hash Table Refresher

Arrays are useful, but only if you have a series of single values.  Hash tables extend arrays by allowing you to have data in the format of Key = Value.

$Countries = @{"Wales" = "Daffodil"; "England" = "Rose"; "Scotland" = "Thistle"; "Ireland" = "Shamrock"}

Note 1: Observe the semi-colon; between each pair.

Note 2: If need be, you could display just the Keys with $Countries.Keys. 

Note 3: Speech marks are only required if the key, or its value, contains a space.

PowerShell 3.0 [Ordered] Command

The new feature of PowerShell v 3.0 hash tables is that you can sort the key using the [Ordered] command see this example:

$Countries = [Ordered]@{"Wales" = "Daffodil"; "England" = "Rose"; "Scotland" = "Thistle"; "Ireland" = "Shamrock"}

This [Ordered] method sorts on the value, e.g.,  Daffodil, Rose, Shamrock and Thistle.

Alternatively, you can use the old .GetEnumerator() method to sort on Name.

$Countries = [ordered]@{"Wales" = "Daffodil"; "England" = "Rose"; "Scotland" = "Thistle"; "Ireland" = "Shamrock"}
$Countries. GetEnumerator() | Sort-Object Name

Hash Table Results

Name Value
———  —–
England  Rose
Ireland   Shamrock
Scotland Thistle
Wales     Daffodil

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Further Research of PowerShell’s Hash Tables

Hashtables are sometimes called dictionaries; whatever the name, and whatever the spelling, you can list the full set of methods and properties by appending | Get-Member.

$Countries = @{"Wales" = "Daffodil"; "England" = "Rose"; "Scotland = "Thistle"; "Ireland" = "Shamrock"}
$Countries | Get-Member

One benefit of creating a hash table is that you can add data, for example:

$Countries.Add("France", "Cockrell")

Note 4: The .Add method requires (Parenthesis) not {curly} brackets.

Footnote: This research solves the mystery of why PowerShell doesn’t have a .Delete method; the reason is because it consistently uses .Remove for this task.

Sorting Number Values in a Hashtable

Here is an alternative to using the [Ordered] command; we need Sort-Object if the values are number rather than text.

$Tennis = @{
    'Mens Singles' = 50;
    'Boys Singles' = 8;
    'Girls Singles' = 7;
    'Mens Doubles' = 33;
    'Womens Singles' = 40;
    'Womens Doubles' = 25;
    'Mixed Doubles' = 16
#$Tennis | Sort-Object value # Will not work
$Tennis.GetEnumerator() | Sort-Object Value -Descending

Learning Points:
Observe the importance of .GetEnumerator.
$Tennis | Sort-Object Value, just would not work, you need that .GetEnumerator() method.

Summary of PowerShell v 3.0 Ordered Hash Table

Another new feature in version 3.0 is [Ordered] hash tables.  Thanks to this one word [ordered] you can achieve a quicker and better solution for sequencing text values than was possible in PowerShell v 2.0.

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See more Microsoft PowerShell v 3.0 examples

PowerShell 3.0  • What’s New in PowerShell 3.0  • PowerShell v 3.0 ISE  • PowerShell Home

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