private void btn_delete_user_Click(object sender, EventArgs e)
        {
            string       user_name    = tb_userName_user.Text.ToString().Trim();
            UserControls userControls = new UserControls();

            if (isValidString(user_name))
            {
                User user = userControls.SearchUser(user_name, "user");
                if (user != null)
                {
                    bool isDeleted = userControls.DeleteUser(user_name, "user");
                    if (isDeleted)
                    {
                        LoadUsers();
                        MessageBox.Show("User Deleted.");
                    }
                    else
                    {
                        MessageBox.Show("User can not be Deleted.");
                    }
                }
                else
                {
                    MessageBox.Show("User Doesn't Exist.");
                }
            }
            else
            {
                MessageBox.Show("Enter User Name.");
            }
        }