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      • Hash Tables

      Hash tables (also called hashtables or dictionaries) are key-value pair collections in PowerShell, similar to associative arrays or dictionaries in other languages.

      1. Creating Hash Tables

      • Basic syntax: 
        $hash = @{
  Name = 'Alice'
  Age = 30
  City = 'New York'
}
      • Empty hash table: 
        $empty = @{}
      • Ordered hash table (preserves insertion order): 
        $ordered = [ordered]@{
  First = 1
  Second = 2
  Third = 3
}

      2. Accessing Values

      $hash['Name']        # Alice
$hash.Name          # Alice (property syntax)
$hash.Age           # 30
$hash['NonExistent']  # Returns $null if key doesn't exist

      3. Adding and Modifying

      $hash['Email'] = 'alice@example.com'  # Add new key
$hash.Age = 31                        # Modify existing key
$hash.Add('Phone', '123-456-7890')    # Add using method

      4. Removing Keys

      $hash.Remove('City')    # Remove by key
$hash.Clear()           # Remove all keys

      5. Checking Existence

      $hash.ContainsKey('Name')    # True
$hash.ContainsValue('Alice') # True
'Name' -in $hash.Keys        # True

      6. Iteration

      # Iterate keys
foreach ($key in $hash.Keys) {
    "$key = $($hash[$key])"
}

# Iterate key-value pairs
$hash.GetEnumerator() | ForEach-Object {
    "$($_.Key) = $($_.Value)"
}

      7. Converting to Objects

      [pscustomobject]$hash    # Convert to custom object
$hash | ConvertTo-Json   # Convert to JSON

      8. Nested Hash Tables

      $nested = @{
    User = @{
        Name = 'Alice'
        Age = 30
    }
    Settings = @{
        Theme = 'Dark'
        Language = 'en'
    }
}
$nested.User.Name    # Alice

      9. Common Use Cases

      • Configuration storage
      • Function parameters (splatting)
      • Grouping data
      • Lookup tables

      10. Performance Notes

      • Hash tables provide O(1) average lookup time
      • For large datasets, consider using [System.Collections.Generic.Dictionary[K,V]] for better performance