Use these two functions to query the supported assemblies [GAC] and .NET Collections (from Windows Powershell in Action, Bruce Payette)

function Get-Assemblies {[AppDomain]::CurrentDomain.GetAssemblies()}

function Get-Types ($Pattern=".") { Get-Assemblies | %{ $_.GetExportedTypes() } | where {$_ -match $Pattern} }

Get-Types System
Get-Types System.Collections
Get-Types System.Collections | more
Get-Types System.Collections.Specialized | more
Get-Types System.Collections.Specialized.StringDictionary
Get-Types System.Collections.Specialized.StringDictionary | gm
Get-Types System.Collections.Specialized.StringDictionary | gm | more