Get-FileSize.ps1

function Get-FileSize {
<#
.Synopsis
   Gets file info, recursively if desired.
.DESCRIPTION
   Enumerates files in a directory getting both the regular
   and compressed size. The enumeration happens in a pipeline
   function so it's memory efficient. The input parameter $Path
   is checked for type so if you pipe the output of Get-ChildItem
   into the function it will use the FullName parameter as the path.
   
   Sean McArdle, Nov 2017
.EXAMPLE
   Get-FileSize $env:temp | select FullName, Length, SizeOnDisk | FT -AutoSize
#>

    [CmdletBinding()]
    [OutputType([PSObject])]
    param (
        [Parameter(Mandatory=$true,
                   ValueFromPipeline=$true,
                   ValueFromPipelineByPropertyName=$true,
                   Position=0)]
        $Path,
        [Parameter(Mandatory=$false,
                   ValueFromPipeline=$true,
                   ValueFromPipelineByPropertyName=$true,
                   Position=1)]
        [switch]$Recurse,
        [switch]$NoCompressCheck
        )
    
    begin {
        
        $ntype =@"
using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
public class NativeHelper_File {
    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern uint GetCompressedFileSizeW([In, MarshalAs(UnmanagedType.LPWStr)] string lpFileName, [Out, MarshalAs(UnmanagedType.U4)] out uint lpFileSizeHigh);

    public static UInt64 GetCompressedFileSize(string FilePath, bool ErrAsZero=false) {
        uint highSize;
        uint lowSize = GetCompressedFileSizeW(FilePath, out highSize);
        int err = Marshal.GetLastWin32Error();
        if (highSize == 0 && lowSize == 0xFFFFFFFF && err != 0) {
            if (ErrAsZero) return 0;
            throw new System.ComponentModel.Win32Exception(err);
        }
        return ((ulong)highSize << 32 | lowSize);
    } 
    
    [DllImport("shlwapi.dll", CharSet = CharSet.Auto)]
    private static extern bool PathCompactPathEx([Out] StringBuilder pszOut, string szPath, int cchMax, int dwFlags);

    public static string PathCompactPath(string Path) {
        StringBuilder sb = new StringBuilder(247);
        PathCompactPathEx(sb, Path, 246, 0);
        return sb.ToString();
    }

    public static IEnumerable<string> GetFiles(string root, string searchPattern, bool Recurse = false) {
        var pending = new Stack<string>();
        pending.Push(root);
        while (pending.Count != 0) {
            var path = pending.Pop();
            string[] next = null;
            try {
                next = Directory.GetFiles(path, searchPattern);
            }
            catch { }
            if (next != null && next.Length != 0)
                foreach (var file in next) yield return file;
            try {
                if (Recurse) {
                    next = Directory.GetDirectories(path);
                    foreach (var subdir in next) pending.Push(subdir);
                }
            }
            catch { }
        }
    }
}
"@
        if(-not ([System.Management.Automation.PSTypeName]'NativeHelper_File').Type) {
            Add-Type -TypeDefinition $ntype -Language CSharp -IgnoreWarnings
        }
    }
    process {
        ## Check if taking in FileInfo objects, 
        $unwrap = $false        
        $unwrap = [bool]($Path.GetType() -like [System.IO.DirectoryInfo])        

        $filter = "*.*"

        $p = [String]::Empty
        if ($unwrap) {
            $p = $Path.FullName
        }
        else {
            $p = $Path
        }
        

        foreach ($fname in [NativeHelper_File]::GetFiles($p, $filter, $Recurse)) {
        
            [UInt64]$size = 0
            [UInt64]$csize = 0

            ## Handle long path name
            if ($fname.Length -gt 247) {
                $fname = [NativeHelper_File]::PathCompactPath($fname)
            }
            
            ## Get FileInfo
            $f = New-Object System.IO.FileInfo $fname               
            
            ## File size on disk
            if ((-not $NoCompressCheck) -and `
                ($f.Attributes.HasFlag([System.IO.FileAttributes]::Compressed))) {
                $csize = $csize + [NativeHelper_File]::GetCompressedFileSize($fname, $true)
            }
            else {
                $csize = $f.Length
            }
            
            $f | Add-Member -MemberType NoteProperty -Name SizeOnDisk -Value $csize -Passthru
        }
    }
}