How can SQLAnywhere's "external CLR" access a System Process - vb.net

Question

In need of an extension in SQLAnywhere (16) to access some DOS functions on the server where the DB is running, I tried :
A first code for a DLL to be called from Sybase
________! SAExternal.vb !____________
Imports System.Diagnostics
Public Class SAExternal
Public Shared Function getDone()
Dim myProcess As Process = System.Diagnostics.Process.Start("notePad.exe", "C:\data\CLR\zTest.txt")
myProcess.WaitForExit()
myProcess.Close()
getDone = "OK"
End Function
End Class
compiled using :
vbc.exe /t:library /out:SAExt.dll SAExternal.vb
Follows some code to test my DLL
_________! SAMain.vb !______________
Module SAMain
Sub Main()
Dim obj as New SAExternal()
MsgBox("Test SAMain " & obj.getDone())
End Sub
End Module
compiled using : vbc.exe /t:winexe /r:SAExt.dll SAMain.vb
SAMain.exe opens correctly notepad.exe, waits until I close it, and comes with the message "Test SAMain OK"
In SQLAnywhere, I coded :
CREATE FUNCTION getDone()
RETURNS LONG VARCHAR
EXTERNAL NAME 'C:\data\CLR\SAExternal\SAExt.dll::SAExternal.getDone() string'
LANGUAGE CLR
Calling the function by "Select getDone()" returns an error :
"Impossible to load the file or assembly 'System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=........' or one of it's denpendencies..."
If I take out the Process part of the SAExternal module:
Public Class SAExternal
Public Shared Function getDone()
getDone = "OK"
End Function
End Class
my function gives me the correct answer ("OK")
For test purposes, I leaved all these files in the same directory as my Database file, including .vb and .dll .
I've searched the web for days to understand what I did wrong, and can't find what I missed.
Could somebody help me ?

Answer 1

try
CREATE FUNCTION getDone() RETURNS LONG VARCHAR
EXTERNAL NAME 'C:\data\CLR\SAExternal\SAExt.dll::SAExternal.getDone() *out* string'
LANGUAGE CLR
Please notice the addition of the out option before string