PowerShell Arrays: The Complete Guide to Collection Management

Understanding PowerShell Arrays

Arrays are fundamental data structures that store collections of items in PowerShell. They can hold elements of any type and are essential for effective scripting and data management.

Array Declaration Basics

# Basic array with values  
$numberArray = 22, 5, 10, 8, 12, 9, 80  

# Empty array initialization  
$emptyArray = @()  

# Range operator array  
$rangeArray = 100..110  

# Mixed-type array  
$mixedArray = "PowerShell", 42, (Get-Date), $true  

Key Property:

$rangeArray.Length  # Returns 11 (100-110 inclusive)  

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Accessing Array Elements

Index-Based Access

PowerShell arrays are zero-indexed:

$rangeArray[0]    # Returns 100 (first element)  
$rangeArray[-1]   # Returns 110 (last element)  
$rangeArray[2..5] # Returns 102,103,104,105 (range)  
$rangeArray[0,3,6] # Returns 100,103,106 (specific indices)  

Iterating Through Arrays

foreach ($number in $rangeArray) {  
    Write-Output "Processing: $number"  
}  

# Alternative with For loop  
for ($i=0; $i -lt $rangeArray.Length; $i++) {  
    Write-Output "Index $i contains $($rangeArray[$i])"  
}  

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Specialized Array Techniques

Strongly Typed Arrays

Enforce data type consistency:

[int[]]$intOnly = 1300, 22, 4578, 8000  
[datetime[]]$dateArray = (Get-Date), "2023-01-01"  

# This will throw an error:  
$intOnly[0] = "string"  

Practical AD Example

$adUsers = @()  
$adUsers = Get-ADUser -Filter * -Properties Mail  

foreach ($user in $adUsers) {  
    if ($user.Mail) {  
        Write-Output "Processing $($user.SamAccountName)"  
    }  
}  

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Array Manipulation

Modifying Elements

# Update by index  
$rangeArray[0] = 200  

# Using SetValue method  
$rangeArray.SetValue(201, 1)  

Adding Elements

# Note: Creates new array (inefficient for large arrays)  
$rangeArray += 500  

# Better alternative for large arrays:  
$list = [System.Collections.ArrayList]::new($rangeArray)  
$list.Add(500) | Out-Null  

Removing Elements

# Create new array without last element  
$trimmedArray = $rangeArray[0..($rangeArray.Length-2)]  

# Filter specific elements  
$filteredArray = $rangeArray | Where-Object { $_ -gt 105 }  

Clearing Arrays

$rangeArray = $null  # Best performance  
Remove-Variable rangeArray  # Alternative method  

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Performance Considerations

1. Array Addition: += creates new arrays - use ArrayList for frequent modifications
2. Large Datasets: Consider [System.Collections.Generic.List[object]] for better performance
3. Memory Management: Explicitly clear large arrays when no longer needed

Pro Tip: For advanced scenarios, explore:

• Multidimensional arrays
• Jagged arrays (arrays of arrays)
• [System.Collections.Specialized.CollectionsUtil]::CreateCaseInsensitiveHashtable()

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