Refresh available ports

Ecosystem
1

We are working on a instrument using the System.IO.Ports library to connect to a COM port on windows.

Everything is working fine, but we can’t get OpenTAP to update the connected devices without restarting the whole program.

The behaviour I would like to see it that when someone clicks on the select box with the list of devices the list gets updated or, even better, catch a event when the connected devices change. So the user always sees a accurate list of available devices to choose from. I tried to use the get methods from the public List<> as wel as the public property which holds the current selected COM port. But with no success.

private List<string> m_AvailablePorts;
public List<string> mAvailablePorts
{
    get {
        m_AvailablePorts = new List<string>( SerialPort.GetPortNames());
        return m_AvailablePorts;
    }
    private set
    {  m_AvailablePorts = value;  }
}

[Display(Name: "COM Port", Group: "Connection", Order: 1.1)]
[AvailableValues( nameof( mAvailablePorts ))]
public string mComPort {
    get {
        m_AvailablePorts = new List<string>( SerialPort.GetPortNames());
        return mComPort;
    }
    set{ mComPort = value; } 
}

What would be the best solution to get a accurate list of currently connected COM port devices?

2

I wouldn’t recommend updating available values from within the getter of mComPort.

I usually structure things as seen below, and I get updated available values every time I click the select button. If it’s not working for you, can you verify that SerialPort.GetPortNames() is returning what you expect?

public List<string> mAvailablePorts
{
    get {
        return new List<string>( SerialPort.GetPortNames());
    }
}

[Display(Name: "COM Port", Group: "Connection", Order: 1.1)]
[AvailableValues( nameof( mAvailablePorts ))]
public string mComPort {get;set;}
1 Like
3

Thanks for your reply.

I tried you solution and the list is updated while the OpenTAP is running but unfortunately it does not update when I click the dropdown. It does update when opening the instrument menu, and changing the value (or any other value in the instrument). And the get function is called 5 times, which seems a little unnecessary, but I think there’s nothing we can do about that (except creating a debounce).

Any chance you know another solution?

4

It may be a bit simplistic, but I’d recommend creating a button in the UI to update the values. This way the user knows what to expect and you don’t create performance issues.

[Display(/*...*/)]
[Browsable(true)]
public void RefreshAvailablePorts(){
   mAvailablePorts = new List<string>( SerialPort.GetPortNames());
}
5

That’s a great idea. However, it will not call the getter to update the list in the UI.

I have done some more digging and found out even when forcefully updating the list using a timer the showed values in the UI will not update. Only when the menu is reloaded (by opening it) or a value is changed new values show. So it seems OpenTAP creates a complete copy of the class to display the menu and only gets new values when changes are made using the interface.

6

Ah you are right, button click does not automatically ensure a gui update. This seems like a mistake.

You can force it by calling ValidatingObject.OnPropertyChanged (so this should work on your object as well.) e.g:

[Display(/*...*/)]
[Browsable(true)]
public void RefreshAvailablePorts(){
   mAvailablePorts = new List<string>( SerialPort.GetPortNames());
 // force the GUI to reload settings values.
  OnPropertyChanged(nameof(mAvailablePorts));
}

Be a bit careful with OnPropertyChanged. It can affect UI performance if called too often.

1 Like
7

This works, thank you!

1 Like