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https://github.com/yevrag35/powershell-listfunctions

A simple module that provides functions to manipulate and search through Arrays, Collections, Lists, and Sets.
https://github.com/yevrag35/powershell-listfunctions

all any hashset list powershell powershell-module

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A simple module that provides functions to manipulate and search through Arrays, Collections, Lists, and Sets.

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# ListFunctions ListFunctions for PowerShell



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This is a simple module that provides functions to manipulate and search through Arrays, Collections, and Lists.  



"ListFunctions" refers to the fact that some the functions are inspired by System.Collections.Generic.List's methods.



## Assert Cmdlets (Any / All)



Sometimes you may want to just check if a specific collection has specific elements in it but don't need them themselves.



### Assert-AnyObject



_Aliases: __Any-Object__, __Any___



This cmdlet returns true or false if at least 1 element in the collection matches a condition - or - if no condition is provided, just if it contains at least 1 element.



If a scriptblock condition is specified, then it will substitute any of the following variables for each element: \$\_, \$this, \$psitem



```powershell

$array = @(1, 2, 3)



if (($array | Any { $_ -gt 2})) {



    # ... at least 1 element is greater than 2.

}



if (($array | Any-Object)) {



    # ... at least 1 element exists.

}

```



### Assert-AllObject(s)



This cmdlet returns true or false indicating whether __all__ elements in a collection match the specified condition.



The scriptblock condition will substitute any of the following variables for each element: \$\_, \$this, \$psitem



```powershell

$array = @(1, 2, 'John')



if (-not ($array | All { $_ -is [int] })) {



    #... at least 1 element is NOT an [int] object.

}

```



---



## Collection Constructors



These cmdlets provide easier ways of constructing the more nuanced, generic types within the `System.Collections.Generic` API namespace.



### New-List



Constructs and returns a list of type `[System.Collections.Generic.List[T]]` where `T` is the generic type defined through the `-GenericType` parameter (defaults to `[object]`).



```powershell

# Create a list of objects with the default capacity (0). 

# Like [System.Collections.ArrayList], objects of *any* type can be added.

$list = New-List



# Create a list of System.Guid objects with an initial capacity of 10,000.

$list = New-List [guid] -Capacity 10000



# Create a list of integers and provide it with the initial values to be added.

$list = @(1, 2, '3') | New-List [int]

# -or-

$list = New-List [int] -InputObject @(3, '100', 56)



```



### New-HashSet



Constructs and returns a list of type [`[System.Collections.Generic.HashSet[T]]`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.hashset-1#remarks "See MS Docs about HashSet[T]") where `T` is the generic type defined through the `-GenericType` parameter (defaults to `[object]`).



This module makes utilizing a HashSet in PowerShell much easier through the use of "ScriptBlock equality comparers". With no pre-compiled or custom-defined `IEqualityComparer[T]` classes necessary, the `New-HashSet` cmdlet lets you define the equality comparison methods through normal PowerShell ScriptBlocks.



Let's say you are importing a CSV where many values of a specific column are duplicates and you only need the first one of each:



```csv

"Id", "Name", "Job"

"1", "John", "The Guy"

"1", "John", "The Guy?"

"2", "Jane", "[redacted]"

```



Using data like this, we can create a custom HashSet where as long as both the `Id` and `Name` columns are the same, the __entire__ object should be treated as the same.



```powershell

$csv = Import-Csv -Path .\Employees.csv



# The equality scriptblock must return a [bool] (true/false) value.

$equality = {   # $left and $right -or- $x and $y -- must be used.

    $left.Name -eq $right.Name -and $left.Id -eq $right.Id

}

# The hashcode scriptblock must return an [int] value.

$hashCode = {   # $_|$this|$psitem -- must be used.

    $name = $_ | Select -ExpandProperty Name | % ToUpper

    $id = ($_ | Select -ExpandProperty Id) -as [int]



    [System.HashCode]::Combine($name, $id)

}



$set = New-HashSet -EqualityScript $equality -HashCodeScript $hashCode -Capacity 2



$set.Add($csv[0])

# Outputs 'true'



$set.Add($csv[1])

# Outputs 'false' and is not added to the set.

```