Question

在C#数据库连接字符串中 这3条是什么意思啊主要是里面的。后面代码看不懂。求大虾帮忙注解下

1、 using (SqlCommand cmd = conn.CreateCommand()
2. using (SqlDataReader reader = cmd.ExecuteReader())
3、 string dbpassword = reader.GetString(reader.GetOrdinal("password"));
全代码是下面：
Console.WriteLine("请输入用户名");
string username = Console.ReadLine();
Console.WriteLine("请输入密码");
string password = Console.ReadLine();
using (SqlConnection conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDBFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True"))
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = "Select * From login where UserName='"+username+"'";
using (SqlDataReader reader = cmd.ExecuteReader())
{
if (reader.Read())
{
string dbpassword = reader.GetString(reader.GetOrdinal("password"));
if (dbpassword == password)
{
Console.WriteLine("登入成功");

}
else
{
Console.WriteLine("登入失败，密码错误");

}
}
else
{
Console.WriteLine("用户名不存在");

}

}
}

}

Answer 1

1. using (SqlCommand cmd = conn.CreateCommand())
定义并实例化命令对象
2. using (SqlDataReader reader = cmd.ExecuteReader())
定义datareader对象并接收cmd对象的执行结果集
3、 string dbpassword = reader.GetString(reader.GetOrdinal("password"));
取得结果集中的password字段的字符值

Answer 2

1、 using (SqlCommand cmd = conn.CreateCommand()///这个地方是创建一个命令对象
2. using (SqlDataReader reader = cmd.ExecuteReader())//执行命令对象的读取方法
3、 string dbpassword = reader.GetString(reader.GetOrdinal("password"));////读取密码这一列的值

Answer 3

1、 创建一个command对象
2. 执行SQL语句读取方法
3、读取密码的值