C#增删改查

SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123");
conn.Open();
//SqlCommand cmd = new SqlCommand(); //构造命令对象
//cmd.Connection = conn;
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = "insert into info values('p005','田泽','0','n004','1990-6-1')";
cmd.ExecuteNonQuery();
conn.Close();
Console.WriteLine("OK");

SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123");//连接类
conn.Open();
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = "select * from info";
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
Console.WriteLine(dr[0].ToString()+dr[1].ToString()+dr[2].ToString()+dr[3].ToString()+dr[4].ToString());
}
conn.Close();

Console.Write("账号：");
string uid = Console.ReadLine();
Console.Write("密码：");
string pwd = Console.ReadLine();
SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123");
conn.Open();
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = "select * from login where username='"+uid+"'and password='"+pwd+"'";
SqlDataReader dr = cmd.ExecuteReader();
if (dr.HasRows==false)
{
Console.WriteLine("输入的用户密码不正确 请重新输入");
}
else
{
Console.WriteLine ("登录成功");
}
conn.Close();