PowerShell の hashtable (System.Collections.Hashtable) と @{} の シリアライズ時 の挙動の違い。

Difference-between-literal-and-new.ps1

$a = @{}
$b = New-Object hashtable
$a['a'] = 1
$a['A'] = 2
$b['a'] = 1
$b['A'] = 2

$a
# Name Value
# ---- -----
# a    2

$b
# Name Value
# ---- -----
# A    2
# a    1


$a | Export-Clixml "$env:TEMP\t.xml"
$c = Import-Clixml "$env:TEMP\t.xml"
$b | Export-Clixml "$env:TEMP\t.xml"
$d = Import-Clixml "$env:TEMP\t.xml"
$c['b'] = 3
$c['B'] = 4
$d['b'] = 3
$d['B'] = 4

$c
# On PowerShell v2
# Name Value
# ---- -----
# b    3
# B    4
# a    2
#
# On PowerShell v4
# Name Value
# ---- -----
# a    2
# b    4



$d
# On PowerShell v2
# Name Value
# ---- -----
# b    3
# B    4
# a    1
# A    2
# 
# On PowerShell v4
# Name Value
# ---- -----
# A    2
# b    3
# a    1
# B    4