#----------------------------------------------------------------
# Md5.ps1
#----------------------------------------------------------------
param
(
  [string]$filespec = $null,
  [bool]$colons = $false
);

#----------------------------------------------------------------
# function Do-Md5
#----------------------------------------------------------------
function Do-Md5()
{
  param
  (
    [string]$filespec = $null,
    [bool]$colons = $false
  );
  
  $hashAlgorithm = new-object -TypeName "System.Security.Cryptography.MD5CryptoServiceProvider";
  
  $files = @(Get-ChildItem -Path $filespec -ErrorAction SilentlyContinue);
  foreach ($file in $files)
  {
    $stream = $file.OpenRead();
    $hashByteArray = $hashAlgorithm.ComputeHash($stream);
    $stream.Close();
    
    $md5StringBuilder = New-Object System.Text.StringBuilder
    
    $hashByteArray | % {
      if ( $colons )
      {
        if ( $md5StringBuilder.Length -gt 0 ) { [void] $md5StringBuilder.Append(":") }
      }
      [void] $md5StringBuilder.Append($_.ToString("x2"))
    }
    
    "MD5($($file.Name))= $($md5StringBuilder.ToString())";

    # Ensure stream is closed if exceptions occurred.
    trap
    {
        if ($stream -ne $null) { $stream.Close(); }
        break;
    }
  }
}

Do-Md5 -filespec $filespec -colons $colons;