private void btnLogin_Click(object sender, EventArgs e)
{
string id = this.txtID.Text;
string pw = this.txtPassword.Text;
SqlParameter[] paras = new SqlParameter[]
{
new SqlParameter("@Id", id),
new SqlParameter("@Password", pw)
};
string sql = "select count(1) from Table1 where Id=@Id and Password=@Password";
int result = (int)DbHelper.ExecuteScalar(sql, paras);
if (result > 0)
{
//MessageBox.Show("login success");
FriendForm ff = new FriendForm();
ff.Show(); //ff.Visible = true;
}
else
{
MessageBox.Show("login failed");
}
}
private void btnLogin_Click(object sender, EventArgs e)
{
string id = this.txtID.Text;
string pw = this.txtPassword.Text;
//Step1: Create database connection object ADO.NET
SqlConnection conn = new SqlConnection("Data Source=LAPTOP-2OJ79OUP;Initial Catalog=test;Integrated Security=True");
//Step2: Open database connnection
conn.Open();
//Step3: Create query object
#region 解释SQL注入
/*
* 如果加这句： ' or 1=1--
* 原本的sql: select count(1) from Table1 where Id = '1001' and Password = '******' 会被变成下面的sql
* select count(1) from Table1 where Id = '1001' and Password = '' or 1=1 --'
* 结局是：竟然可以成功登录！这就是如果你熟悉sql语句，可以“破解”的地方！
*/
#endregion
//防止SQL注入：使用变量和参数化：把特殊符号（比如')转义成普通字符串
SqlParameter para1 = new SqlParameter("@Id", id); //using System.Data.SqlClient;
SqlParameter para2 = new SqlParameter("@Password", pw);
#region 高级写法：用数组；就不用写那么多参数
/*
* SqlParameter[] paras = new SqlParameter[]
* {
* new SqlParameter("@Id",id),
* new SqlParameter("@Password", pw)
* };
*/
#endregion
/* 原本的这句不要了：
* string sql = $"select count(1) from Table1 where Id='{id}' and Password='******'"; //count(1)的1代表地是 伪列 （“不是实际的列”：不是指第一个列名id）
*/
string sql = "select count(1) from Table1 where Id=@Id and Password=@Password";
SqlCommand command = new SqlCommand(sql, conn);
command.Parameters.Add(para1);
command.Parameters.Add(para2);
#region 高级写法：用数组；就不用写那么多参数
/*
* 丢弃：
* command.Parameters.Add(para1);
* command.Parameters.Add(para2);
* 改用：
* command.Parameters.AddRange(paras);
*/
#endregion
//Step4: Run query
/*
* command.ExecuteNonQuery(); //add, delete, edit
* command.ExecuteReader(); //query will return multiple rows and columns
*/
int result = (int)command.ExecuteScalar(); //query will return first row and first column
if (result > 0)
{
//MessageBox.Show("login success");
FriendForm ff = new FriendForm();
ff.Show(); //ff.Visible = true;
}
else
{
MessageBox.Show("login failed");
}
//Step5: close connection
conn.Close();
}