private void sign_in_Click(object sender, EventArgs e)
{
String username, password;
username = txtName.Text;
password = txtpsd.Text;
String myconn = "server = localhost;port=3306;user=root;password=123456;database=book";//数据库实例连接字符串
MySqlConnection sq = new MySqlConnection(myconn);//建立连接
sq.Open();//打开数据库
string sql = string.Format("select count(*) from users where user_name='{0}'", username);
MySqlCommand cmd = new MySqlCommand(sql, sq);
int a = Convert.ToInt32(cmd.ExecuteScalar());//返回一个值，看用户是否存在
string sql1 = string.Format("select count(*) from users where password='******'", password);
MySqlCommand cmd1 = new MySqlCommand(sql1, sq);
int b = Convert.ToInt32(cmd1.ExecuteScalar());
if(a !=0 &&b!=0)
{
Form1 form = new Form1();
form.Show();
}
else
{
DialogResult dr = MessageBox.Show("请检查您的用户名或密码是否正确，或注册新用户！","登录失败!",MessageBoxButtons.YesNo,MessageBoxIcon.Question);
if(dr == DialogResult.Yes)//打开注册页面
{
Lign_up form2 = new Lign_up();
form2.Show();
}
else
{
this.Show();
}
}
}
private void sign_up_Click(object sender, EventArgs e)
{
Lign_up form2 = new Lign_up();
form2.Show();
}