Generic type of Generic Type in Powershell

Question

Well generics in Powershel are quite confusing. To instantiate a simple List you need to dance around with a tambourine:

$type = ("System.Collections.Generic.List"+'`'+"1") -as "Type"
$type= $type.MakeGenericType("System.string" -as "Type")
$o = [Activator]::CreateInstance($type)

But what if I need something a bit more complex like: <Dictionary<string,List<Foo>> for example

or for example here: Dictionary<string,List<string>>

$listType = ("System.Collections.Generic.List"+'`'+"1") -as "Type"
$listType = $listType.MakeGenericType("System.string" -as "Type")
$L = [Activator]::CreateInstance($listType)

$dicType = ("System.Collections.Generic.Dictionary"+'`'+"2") -as "Type"

#the next line is problematic
$dicType = $dicType.MakeGenericType( 
     @( ("system.string" -as "Type"), 
        ("System.Collections.Generic.List" as "Type)) # and that's of course wrong
      )

$D = [Activator]::CreateInstance($dicType )

Answer 1

While you can delve into CLR internal representations and make life hard for yourself, you don't have to:

$dict = new-object 'collections.generic.dictionary[string,int]'
$dict.add("answer", 42)

Want a type literal representation?

[collections.generic.dictonary[string,int]]

Done. How about generic type parameters?

$dictOfList = new-object 'collections.generic.dictionary[string,
    [collections.generic.list[int]]]'

Done.

However, there's an unfortunate catch. In PowerShell 2.0, there's a bug when you mix and match BCL and 3rd party types as type parameters. The latter need to be assembly qualified:

# broken over two lines for clarity with backtick escape
$o = new-object ('collections.generic.dictionary[[{0}],[{1}]]' -f `
        [type1].fullname, [type2].fullname)

Hope this helps. In PowerShell 3.0, this has been fixed.