从事件处理程序进行更新时，即使触发了Property Changed，MVVM View绑定也不会更新

Question

I face the following issue: I use a class to encapsulate serial port operation as following:

 public class SNScanner : IDisposable
{
    public string COMPort { get; set; }
    public int Baudrate { get; set; }
    SerialPort sp;
    string Rsv;
    public SNScanner(string cOMPort, int bauderate)
    {
        COMPort = cOMPort;
        Baudrate = bauderate;
        sp = new SerialPort()
        {
            PortName = COMPort,
            BaudRate = Baudrate,
            DataBits = 8,
            StopBits = StopBits.One,
            Parity = Parity.None
        };
        sp.DataReceived += Sp_DataReceived;
        if (!sp.IsOpen)
        {
            sp.Open();
        }
    }

    private void Sp_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        Thread.Sleep(100);
        Rsv = string.Empty;
        Rsv = sp.ReadExisting();
        if (!string.IsNullOrEmpty(Rsv) && Rsv.Length == 17 )
        {
            OnSerialNumberDetected(new SerialNumberDetectedEventArgs {
                SerialNumber = Rsv.Substring(1,15) });
        }
    }



    #region Serial number detected event
    public event EventHandler SerialNumberDetected;

    protected virtual void OnSerialNumberDetected(EventArgs e) => SerialNumberDetected?.Invoke(this, e);

    public void Dispose()
    {
        sp.Close();
        try
        {
            sp.Dispose();
        }
        catch (Exception)
        {

        }
    }


    #endregion
}
public class SerialNumberDetectedEventArgs : EventArgs
{
    public string SerialNumber { get; set; }
}

when it detect a correct serial number that meet my criteria it fires onSerialNumberDetected event. In the view model i superscribe to this event as following:

        myscanner = new SNScanner("COM3", 9600);
        SerialNumber = "Empty";
        myscanner .SerialNumberDetected += myscanner_SerialNumberDetected;

    }

    private void myscanner_SerialNumberDetected(object sender, EventArgs e)
    {
        SerialNumber = ((SerialNumberDetectedEventArgs)e).SerialNumber;
    }


    private string _sn;

    public string SerialNumber
    {
        get { return _sn; }
        set { _sn = value; NotifyPropertyChanged(nameof(_sn)); }
    }

My view binding as following

<Window.DataContext>
    <local:mvm/>
</Window.DataContext>    
<Label FontFamily="Console"
                    FontSize="20"
                    Content="{Binding SerialNumber}"
                    Margin="5"
                    VerticalAlignment="Center"
                    Width="400"/>

During debugging the view model can receive the SerialNumber from the event but the view does not update.

Answer 1

You are notifying wrong property name:

    public string SerialNumber
    {
        get { return _sn; }
        set { _sn = value; NotifyPropertyChanged(nameof(_sn)); }
    }

Instead of NotifyPropertyChanged(nameof(_sn)) should be NotifyPropertyChanged(nameof(SerialNumber));