Question

I am learning c# and I would like to know why my code won’t add a row to my DataGridView in the ReceivePacket area. It works in the SendPacket but not in the other.
The purpose is to simply send a UDP packet to a machine, thanks in advance.
Here is my code:

private void btnSend_Click(object sender, EventArgs e)
        {
            SendPacket();
        }
        private void btnReceiving_Click(object sender, EventArgs e)
        {
            Thread thread = new Thread(new ThreadStart(reciev));
            thread.Start();
        }    

UdpClient client = new UdpClient();

        public void SendPacket()
        {
            byte[] packet = Encoding.ASCII.GetBytes(DateTime.Now.ToString("HH:mm:ss:ff"));
            client.Send(packet, packet.Length, tbIP.Text, 444);
            dgvSend.Rows.Add(DateTime.Now.ToString("HH:mm:ss:ff"));
        }

        public void ReceivePacket(byte[] packet)
        {// it goes wrong here, because it gives a crossthread error
            dgvReceiv.Rows.Add(Encoding.ASCII.GetString(packet), DateTime.Now.ToString("HH:mm:ss:ff"));
        }

        public void reciev()
        {
            UdpClient client = new UdpClient(444);
            while (true)
            {
                IPEndPoint server = new IPEndPoint(IPAddress.Any, 0);
                byte[] packet = client.Receive(ref server);
                ReceivePacket(packet);
            }
        }

I fixed it using this line of code instead of the normal (with the invoke 🙂 ):

dgvReceiv.Invoke(new MethodInvoker(delegate { dgvReceiv.Rows.Add(Encoding.ASCII.GetString(packet), DateTime.Now.ToString("HH:mm:ss:ff")); }));

Answer 1

Here you go example of using delegates to invoke actions from other threads on controls created on main thread.

http://msdn.microsoft.com/en-us/library/zyzhdc6b.aspx