private void label4_Click(object sender, EventArgs e)
        {
            user_history form = new user_history();

            form.Show();
            this.Dispose();
        }
        private void button3_Click(object sender, EventArgs e)
        {
            //界面替换  点击查询历史按钮 进入历史界面
            user_history form = new user_history();

            form.Show();
            this.Dispose();
        }