SqlDataReader 用法

获得数据库的密码，并且与输入的值比较：

using(SqlDataReader reader=cmd.ExecuteReader())

{

if(reader.Reader())

{//获得数据库的密码

string dbpassword=reader.GetString(reader.GetOrdinal("Password"));

if(password==dbpassword)//Comparing the Password what's

{

Console.WriteLine("登入成功！");

Console.WriteLine(reader.GetString(1));//读取第一列数据

}

}

}

reader的GetString,GetInt32等方法只接受整数参数，也就是序列号，用GetOrdinal方法根据列名动态得到序号

一个登入的后台：

using(SqlConnection conn=new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDBFilename=|DataDirectory|\MyDB.mdf;Integrated Security=true;User Instance=True"))

{

conn.Open();

using(SqlCommand cmd=conn.CreateCommand())

{

cmd.CommandText="select * from T_User where UserName=@username";

cmd.Parameters.Add(new SqlParameter("username",txtUserName.Text));

using(SqlDataReader reader=cmd.ExecuteReader())

{

if(reader.Read())

{

int errorTimes=reader.GetInt32(reader.GetOrdinal("ErrorTimes"));

if(errorTimes>3)

{

MessageBox.Show("登入错误次数过多，禁止登入！");

return;

}

string dbpasswoord=reader.GetString(reader.GetOrdinal("Password"));

if(dbpassword==txtPassword.Text)

{

MessageBox.Show("登入成功！");

}

else

{

using(SqlCommand updateCmd=conn.CreateCommand())

{

updateCmd.CommandText="update T_User Set ErrorTimes=ErrorTimes+1 where UserName=@UserName";

updateCmd.Parameters.Add(new SqlParameter("UserName"，txtUserName.TEXT));

updateCmd.ExecuteNonQuery();

}

MessageBox.Show("登入失败！");

}

}

else

{

MessageBox.Show("用户名不存在！");

}

}

}

}