Calling .Net functions

I'm trying to write a script that does a SHA1 check on a file and I understand the .Net calls that I need to call but for the life of me I can't get it working in maxscript. Can anyone help me finish it?

The first problem is the file delme#.txt never gets closed. I'm pretty sure I need to call stream.Close() but I can't get it to work.

The second is running byte[] = hashClass.ComputeHash(fileStream, FileMode.Open)
How do I store a byte array in maxscript?

fn SHA filename =
(
	if doesFileExist filename then
	(
	
		fileMode = dotNetClass "System.IO.FileMode"
		print (fileMode.Open as string)
		
		stream = dotNetObject "System.IO.FileStream" filename fileMode.Open
		
		hashClass = dotNetClass "System.Security.Cryptography.SHA1CryptoServiceProvider" 
		hash = hashClass.ComputeHash stream
		
		-- Try unsucessfully to close the stream
		
		showMethods stream
		dotNetObject "System.Security.Cryptography.SHA1CryptoServiceProvider.Close"
		dotNetObject "System.IO.FileStream.Close"
		
	)
)

SHA "c:/DelMe6.txt"