函数调用如下：
        private void txtCmdInput_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                e.SuppressKeyPress = true;    / /回车事件已经处理完不再响应了
                string str = GetCmd(txtCmdInput);
                MoveCmdToLast(txtCmdInput, str);
            }
        }