Passing bytes as parameter to c#?

Question

I am currently stuck while trying to call a c# methods from python. I am using python 3.2 and not IronPython. I used pip to install the latest version of python.net

Problem occurs (as often discussed) while using ref or out parameters.

Here is my code so far:

import clr

path = clr.FindAssembly("USB_Adapter_Driver")
clr.AddReference(path)
from USB_Adapter_Driver import USB_Adapter
gpio = USB_Adapter()

version2 = ''
status, version = gpio.version(version2)
print ('status: ' + str(status))
print ('Version: ' + str(version))

readMask = bytearray([1])
writeData = bytearray([0])

print (readMask)
print (writeData)

status, readData = gpio.gpioReadWrite(b'\x01',b'\x00',b'\x00')
status, readData = gpio.gpioReadWrite(readMask[0],writeData[0],b'\x00')
status, readData = gpio.gpioReadWrite(readMask[0],writeData[0],)

I have had some major issues getting clr. running at all. But in this exact config it seems to work (I need to save the path to a variable, otherwise it wont work, I also cant type the path the dll in clr.AddReference(path) because this wont work as well)

The c# version method looks like this:

public USB_Adapter_Driver.USB_Adapter.Status version(ref string ver)

My status variable gets a value which works perfectly with the status enum for the c# class.

Problem is: after the call my variable "version" is empty. Why? According to: How to use a .NET method which modifies in place in Python? this should be a legal way to do things. I also tried to use the explicit version but my namespace clr does not contain clr.Reference().

The next (and more severe) problem is pio.gpioReadWrite().Here the info about this one:

public USB_Adapter_Driver.USB_Adapter.Status gpioReadWrite(byte readMask, byte writeData, ref byte readData)

Here I get the error message:

TypeError: No method matches given arguments

It doesn't matter which of the calls I use from above. All of them fail.

Here is the full output of a debugging run:

d:\[project path]\tests.py(6)<module>()
status: 6
Version: 
bytearray(b'\x01')
bytearray(b'\x00')
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
d:\[project path]\tests.py(28)<module>()
status, readData = gpio.gpioReadWrite(readMask[0],writeData[0],)
(Pdb) Traceback (most recent call last):
  File "D:\WinPython-64bit-3.4.4.2Qt5\python-3.4.4.amd64\lib\pdb.py", line 1661, in main
    pdb._runscript(mainpyfile)
  File "D:\WinPython-64bit-3.4.4.2Qt5\python-3.4.4.amd64\lib\pdb.py", line 1542, in _runscript
    self.run(statement)
  File "D:\WinPython-64bit-3.4.4.2Qt5\python-3.4.4.amd64\lib\bdb.py", line 431, in run
    exec(cmd, globals, locals)
  File "<string>", line 1, in <module>
  File "d:\[project path]\tests.py", line 28, in <module>
    status, readData = gpio.gpioReadWrite(readMask[0],writeData[0],)
TypeError: No method matches given arguments

Hope one of you has an idea on how to fix this.

Thanks, Kevin

Answer 1

Python.Net doesn't handle ref/out parameters like IronPython.
status, readData = gpio.gpioReadWrite(b'\x01',b'\x00',b'\x00') call is not quite correct since Python.Net will not return an updated readData as second result.
You can handle ref parameters using reflection. Check out my answer to similar question here

there is a rough code template for your case:

import clr
clr.AddReference("USB_Adapter_Driver")
import System
import USB_Adapter_Driver

myClassType = System.Type.GetType("USB_Adapter_Driver.USB_Adapter, USB_Adapter_Driver") 
method = myClassType.GetMethod("gpioReadWrite")
parameters = System.Array[System.Object]([System.Byte(1),System.Byte(0),System.Byte(0)])
gpio = USB_Adapter_Driver.USB_Adapter()
status = method.Invoke(gpio,parameters)
readData = parameters[2]