private void button1_Click(object sender, EventArgs e)
        {

            string userid = "asdfjkl";//定义一个用户名
            string password = "123";//定义密码

            if (txtUserId.Text == userid && txtpwd.Text == password)
            {

               // MessageBox.Show("登陆成功！");
                this.Hide();
                Form1 form = new Form1();
                form.Show();
            }
            else
            {
                MessageBox.Show("错误，你还可以输入"+(2-count)+"次！");
                count = count + 1;
            }


            if (count == 3)
                this.Close();
        }
        private void denglu_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyCode == Keys.Return) ;
            {
                button1_Click();
            }
        }

private void denglu_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyCode == Keys.Return) ;
            {
                 this.button1.PerformClick();            }
        }