Display online users except the current logged in user in ASP.Net Membership

I have below code to display "list of all the online users" inside listBox using Membership function.

Code:

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            MembershipUserCollection allUser = Membership.GetAllUsers(); // to get all the users
            List<MembershipUser> onlineUsers = new List<MembershipUser>(); //creating list of online users         
            
            foreach (MembershipUser user in allUser)
            {
                if (user.IsOnline)
                {
                    onlineUsers.Add(user);
                }
            }
            Lbl_NumOfOnline_User.Text = (Membership.GetNumberOfUsersOnline()).ToString(); //return no. of online user
            lst_Users.DataSource = onlineUsers; //return online users
            //lst_Users.DataSource = allUser; // return all the users
            lst_Users.DataBind();

    }

I want to remove that user from the list of online users, who himself has logged in. Example: if I had logged-in with UserName: Admin, then this Admin should not show to me in the list of "online users"

Tried below Code but not working:

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            MembershipUserCollection allUser = Membership.GetAllUsers(); // to get all the users
            List<MembershipUser> onlineUsers = new List<MembershipUser>(); //creating list of online users         
            MembershipUser m_user = Membership.GetUser(); //to get self logged-in user

            Session["UName"] = m_user.UserName.ToString();
            if (m_user != null)
            {
                onlineUsers.Remove(m_user);
            }

            foreach (MembershipUser user in allUser)
            {
                if (user.IsOnline)
                {
                    onlineUsers.Add(user);
                }
            }
            Lbl_NumOfOnline_User.Text = (Membership.GetNumberOfUsersOnline()).ToString(); //return no. of online user
            lst_Users.DataSource = onlineUsers; //return online users
            //lst_Users.DataSource = allUser; // return all the users
            lst_Users.DataBind();

    }