c# event handler is called multiple times when event is raised once

Question

Below is my code, first is where I raise the event and second section is where I consume it in another class. It seems pretty straight forward, but the logs are showing that even though the event is raised once, the event is firing 20+ times on the class that consumes this event. Any ideas?

IBSerialPort class:

public delegate void PacketReceivedHandler(object sender, PacketReceivedEventArgs e);
public event PacketReceivedHandler OnPacketReceived;

public class PacketReceivedEventArgs : EventArgs
{
  public Packet PacketReceived { get; private set; }

  public PacketReceivedEventArgs(Packet packet)
  {
    PacketReceived = packet;
  }
}

// raise event
if (OnPacketReceived != null)
{
    Log("This is only called ONCE!");
    PacketReceivedEventArgs args = new PacketReceivedEventArgs(data);
    OnPacketReceived(this, args);
}

Class that uses IBSerialPort and consumes its OnPacketReceived Event:

IBSerialPort ibSerialPort = null;
..
if (ibSerialPort == null)
{
  Log("This is only called once");

  ibSerialPort = IBSerialPort.Instance;

  ibSerialPort.OnPacketReceived += ibSerialPort_OnPacketReceived;
}

void ibSerialPort_OnPacketReceived(object sender, IBSerialPort.PacketReceivedEventArgs args)
{
   Log("This is called ~25 times!!!!");
}

Answer 1

Try this, this will unregister any prev subscriber:

ibSerialPort.OnPacketReceived -= ibSerialPort_OnPacketReceived;   // unregister
ibSerialPort.OnPacketReceived += ibSerialPort_OnPacketReceived;  //register