Skip optional arguments when calling DLLs via .NET assemblies in PowerShell

I am trying to call the CascadeWindows DLL from PowerShell. The documentation (https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-cascadewindows) states that there are optional parameters (an HWND/IntPtr, an array of HWND/IntPtrs, and a RECT), which can be NULL. How do I get PowerShell to call this with those parameters as NULL?

$cw = Add-Type -MemberDefinition '[DllImport("user32.dll")] public static extern ushort CascadeWindows(IntPtr hwndParent, uint wHow, IntPtr lpRect, uint cKids, IntPtr [] lpKids);' -Name 'Cascad' -Namespace 'Win32' -PassThru
# Fails with error, 'Cannot find an overload for "CascadeWindows" and the argument count: "2".'
$cw::CascadeWindows(0,0) 
# Returns 0, i.e. fails. Error code is 203, 'The system could not find the environment option that was entered.'
$cw::CascadeWindows(0,0,0,0,0) 
$gle = Add-Type -MemberDefinition '[DllImport("kernel32.dll")] public static extern uint GetLastError();' -Name 'gle' -Namespace 'Win32' -PassThru
$gle::GetLastError()

You can use IntPtr.Zero for optional IntPtr P/Invoke parameters:

$cw::CascadeWindows(
    [IntPtr]::Zero,
    [uint32] 0,
    [IntPtr]::Zero,
    [uint32] 0,
    $null)

As for your implementation, here is how I would do it. Note that the [in] wHow argument is actually a flag:

Add-Type '
using System;
using System.ComponentModel;
using System.Runtime.InteropServices;

namespace Win32
{
    [Flags]
    public enum CascadeFlags : uint
    {
        MDITILE_SKIPDISABLED = 0x0002,
        MDITILE_ZORDER = 0x0004
    }

    public static class Cascade
    {
        [DllImport("user32.dll", EntryPoint = "CascadeWindows", SetLastError = true)]
        private static extern ushort NativeCascadeWindows(
            IntPtr hwndParent,
            uint wHow,
            IntPtr lpRect,
            uint cKids,
            IntPtr[] lpKids);

        public static ushort CascadeWindows(
            IntPtr hwndParent,
            CascadeFlags wHow,
            IntPtr lpRect,
            uint cKids,
            IntPtr[] lpKids)
        {
            ushort result = NativeCascadeWindows(hwndParent, (uint)wHow, lpRect, cKids, lpKids);
            if (result != 0)
            {
                return result;
            }

            throw new Win32Exception();
        }
    }
}'

[Win32.Cascade]::CascadeWindows(
    [IntPtr]::Zero,
    [Win32.CascadeFlags]::MDITILE_SKIPDISABLED,
    [IntPtr]::Zero,
    [uint32] 0,
    $null)