object GattCharacteristic.Value crash with 'System.ArgumentException'

[anonimysUA]

Im make Windows Console Application and try communicate with BLE device by UART (by TX-trancieve RX-recieve chanels), but have 2 Issue for get TX result:

1. Event CharacteristicValueChanged never triggered
2. tx_char.Value crash (same with call ReadValueAsync())

IReadOnlyList<GattCharacteristic> characteristics = null;
GattCharacteristic rx_char = null;
GattCharacteristic tx_char = null;

// I. Get a Service
Task.Run(async () =>
{
    List<GattService> availableServices = await token.device.Gatt.GetPrimaryServicesAsync(null);// .GetPrimaryServiceAsync(GattServiceUuids.Battery);
    rx_service = availableServices.First(x => x.Uuid.Value == RX_SERVICE_UUID);
}).GetAwaiter().GetResult();

// II. Get a characteristic
Task.Run(async () =>
{
    characteristics = await rx_service.GetCharacteristicsAsync();                         
}).GetAwaiter().GetResult();

for (int i = 0; i < characteristics.Count; i++)
{
    if(characteristics[i].Uuid.Value.Equals(ST338BLE_Const.RX_CHAR_UUID))
    {
        rx_char = characteristics[i];
        rx_char.CharacteristicValueChanged += RX_CharacteristicValueChanged;
        //rx_char.StartNotificationsAsync();
    }
    else if(characteristics[i].Uuid.Value.Equals(ST338BLE_Const.TX_CHAR_UUID))
    {
        tx_char = characteristics[i];
        tx_char.CharacteristicValueChanged += TX_CharacteristicValueChanged;
        tx_char.StartNotificationsAsync();
    }
}   

// III. Send
Task.Run(async () => 
{
    await rx_char.WriteValueWithResponseAsync(new byte[]{ /*APDU command*/ });    
}).GetAwaiter().GetResult();

// IV. Try to Receive data
                    
byte[] rec = tx_char.Value; // Crash when try read a result    

// The same Crash result
//Task.Run(async () =>
//{
//    rec = await tx_char.ReadValueAsync();
//}).GetAwaiter().GetResult();

Additional info:
Exception thrown 'System.ArgumentException'

StackTrace
"at System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeBufferExtensions.ToArray(IBuffer source, UInt32 sourceIndex, Int32 count)\r\n
at InTheHand.Bluetooth.GattCharacteristic.PlatformGetValue()\r\n
..."

• Win 11 Pro
• .Net Framework 4.6.1.
• InTheHand.Net.Bluetooth 4.1.0.0 (Runtime v4.0.30319)

[peterfoot]

can you query the Properties of both characteristics to confirm what features they support?

[anonimysUA]

can you query the Properties of both characteristics to confirm what features they support?

Im use that UUID of service/tx/rx on my native iOS/Android libs, so im sure they are supported and work.

Maybe my code belowe wrong for a get answer from device?

Task.Run(async () =>
{
    rec = await tx_char.ReadValueAsync();
}).GetAwaiter().GetResult();

How a right way i can get result after send a APDU command to device?

[cogree]

I was able to get reproduce this error; it seems related to characteristics that produce a zero byte response.

This quick example illustrates the cause (I think):

 uint capacity = 0;
 var buffer = new Windows.Storage.Streams.Buffer(capacity);
 buffer.ToArray();
 // System.ArgumentException: 'The specified buffer index is not within the buffer capacity. '