problem refresh listbox c#

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C#

sockets

Hi. i made a chat but now i have a problem with refresh userList after a user disconnect. I tried (userList.Items.Cout -1) but is not working. Any ideas? Thanks.

public partial class PublicChatForm : Form
    {
        
        public PublicChatForm()
        {
            pChat = new PrivateChatForm(this);
            InitializeComponent();
        }
        
        public readonly LoginForm formLogin = new LoginForm();

        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);
            formLogin.Client.Received += _client_Received;
            formLogin.Client.Disconnected += Client_Disconnected;
            Text = "TCP Chat - " + formLogin.txtIP.Text + " - (Conectat ca: " + "user" + ")";
            formLogin.ShowDialog();
        }

        public static void Client_Disconnected(ClientSettings cs)
        {
    
        }

        private readonly PrivateChatForm pChat;

        public void _client_Received(ClientSettings cs, string received)
        {
            var cmd = received.Split('|');
            switch (cmd[0])
            {
                case "Users":
                    this.Invoke(() =>
                    {
                        userList.Items.Clear();
                        for (int i = 1; i < cmd.Length; i++)
                        {
                            if (cmd[i] != "Connected" | cmd[i] != "RefreshChat")
                            {
                                userList.Items.Add(cmd[i]);
                            }
                            
                        }
                    });
                    break;
                case "Message":
                    this.Invoke(() =>
                    {
                        txtReceive.Text += cmd[1] + "\r\n";
                    });
                    break;
                case "RefreshChat":
                    this.Invoke(() =>
                    {
                        txtReceive.Text = cmd[1];
                    });
                    break;
                case "Chat":
                    this.Invoke(() =>
                    {
                        pChat.Text = pChat.Text.Replace("user", formLogin.txtNickname.Text);
                        pChat.Show();
                    });
                    break;
                case "pMessage":
                    this.Invoke(() =>
                    {
                        pChat.txtReceive.Text += "Server says: " + cmd[1] + "\r\n";
                    });
                    break;
                case "List":
                    userList.Items.AddRange(txtReceive.Text.Split('*'));
                    userList.Items.RemoveAt(userList.Items.Count - 1);
                    break;
                case "Disconnect":
                    userList.Items.RemoveAt(userList.Items.Count - 1);
                    Application.Exit();
                    
                    break;
            }
        }

        private void btnSend_Click(object sender, EventArgs e)
        {
            if (txtInput.Text != string.Empty)
            {
                formLogin.Client.Send("Message|" + formLogin.txtNickname.Text + "|" + txtInput.Text);
                txtReceive.Text += formLogin.txtNickname.Text + " says: " + txtInput.Text + "\r";
                txtInput.Text = string.Empty;
            }
        }