MidiDeviceException: Internal error (IN_GETPROPERTYRESULT_UNKNOWNERROR) when accessing InputDevice.Name

[BlackCoyote]

Hey,

I'm having a user report the following error from my app:

Melanchall.DryWetMidi.Multimedia.MidiDeviceException: Internal error (IN_GETPROPERTYRESULT_UNKNOWNERROR).
   at Melanchall.DryWetMidi.Multimedia.NativeApi.HandleResult[TResult,TException](TResult result, Func`3 createException)
   at Melanchall.DryWetMidi.Multimedia.InputDevice.get_Name()
   at C.CC.A.a()

I've tried making sure the Device.Name property could be accessed safely before opening and listening to a device, but it seems to be able to get the error at any point during runtime for previously working devices.

Do you know what causes this exception? Could I be using the API incorrectly, or is there a clean way to safely handle or avoid this exception?

Thanks!
Sander

[melanchall]

Hi Sander,

Well, from what I see, the user is on macOS. This error means GetDevicePropertyValue system function has returned code that doesn't indicate success and it's not in the list of errors I know:

OSStatus status = GetDevicePropertyValue(inputDeviceInfo->endpointRef, propertyID, value);
if (status != noErr)
{
    switch (status)
    {
        case kMIDIUnknownEndpoint: return IN_GETPROPERTYRESULT_UNKNOWNENDPOINT;
        case SMALL_BUFFER_ERROR: return IN_GETPROPERTYRESULT_TOOLONG;
        case kMIDIUnknownProperty: return IN_GETPROPERTYRESULT_UNKNOWNPROPERTY;
    }
        
    return IN_GETPROPERTYRESULT_UNKNOWNERROR;
}
    
return IN_GETPROPERTYRESULT_OK;

How often this error is reproduced? Always, sometimes, from the start of device usage?

As a workaround I can suggest you to store Name in your app right after connecting to the device and then just return cached value without calling Device.Name. I'm pretty sure the name of the device won't change during working with it and so this approach should be safe. But this will work only if first call of Name property doesn't fail.

But my answer is something went wrong with the device or the system function of macOS. Unfortunately I don't know full list of error codes that can be returned by GetDevicePropertyValue function. But I'll probably add a parameter to return exact code in case of something unexpected.

[BlackCoyote]

Hey,

The user reports the issue as happening sporadically with no discernable pattern. It seems to happen randomly at any given time while their device is connected.

Thank you for the info and the suggestion!