SerialPort and MVVM - mvvm

Question

I'm trying to understand MVVM when using I/O, specifically a serial port.
I've implemented my MVVM Model as follows:
Model
public class SerialPortModel
{
private SerialPort Port;
public SerialPortModel()
{
Port = new SerialPort
{
Handshake = Handshake.None,
BaudRate = 9600,
ReadTimeout = 400,
DiscardNull = false,
ReceivedBytesThreshold = 1,
WriteTimeout = 100
};
}
}
My question is:
Should I implement methods such as getting port names, open and close port, etc in the Model or in the ViewModel?
I've read that the Model should just contain data, and not methods?
Or is it OK for the Model to run methods such as opening the COM port?

Answer 1

I wouldn't use it in either. The model should contain meaningful data which in this case would be the data that you are reading from the serial port. A good approach is to make an object that abstracts what you are affecting on the target device.
Let's say you're working with one of the digital scales that have a serial port. You would want methods to read the current weight and set the current time through methods. This keeps all your serialization and deserialization in one spot so you're not passing around a port, raw bytes, or other things. Here is a sample (details, error handling elided):
// Model
public class WeightReport
{
public float Weight { get; set; }
public string Units {get; set; }
}
// Port service
public class MyScale
{
private SerialPort _port;
public MyScale()
{ /* Setup port */ }
public WeightReport ReadWeightReport()
{
var resp = _port.ReadBytes(/* however many bytes */);
// or make a factory, static parser, whatever
var report = new WeightReport(resp);
return report;
}
}
// ViewModel
public class MyViewModel
{
private MyScale _scale;
public WeightReport LastRead { get; set; }
// Add events, delegates, background thread, methods etc. to update LastRead
}
Of course there many ways to do this and it really comes down to your style and how much you expect to maintain this application.