小编Sof*_*per的帖子

我正在使用此代码但不工作并抛出此异常:对​​象引用未设置为对象设备[0]的实例,为我提供空值.

   private async void ConnectToSerialPort()
    {
        string selector = SerialDevice.GetDeviceSelector("COM7");
        DeviceInformationCollection devices = await DeviceInformation.FindAllAsync(selector);
        if (devices.Count > 0)
        {
            DeviceInformation deviceInfo = devices[0];
            SerialDevice serialDevice = await SerialDevice.FromIdAsync(deviceInfo.Id);
            Debug.WriteLine(serialDevice);
            serialDevice.BaudRate = 9600;
            serialDevice.DataBits = 8;
            serialDevice.StopBits = SerialStopBitCount.Two;
            serialDevice.Parity = SerialParity.None;

            DataWriter dataWriter = new DataWriter(serialDevice.OutputStream);
            dataWriter.WriteString("your message here");
            await dataWriter.StoreAsync();
            dataWriter.DetachStream();
            dataWriter = null;
        }
        else
        {
            MessageDialog popup = new MessageDialog("Sorry, no device found.");
            await popup.ShowAsync();
        }
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        ConnectToSerialPort();
    } …