Question

我尝试查看我的代码几个小时试图查看我哪里出错了，谷歌似乎也找不到答案。基本上我运行的是这段代码：

public bool LoginRequest(string ReceivedUsername, string ReceivedPassword)
    {

        bool ValidLogin = false;

        try
        {

            using (SqlConnection myConnection = new SqlConnection(ConnectString))
            {
                myConnection.Open();
                Log.Debug("Succesful sql connection");
                SqlCommand userSELECTcom = new SqlCommand("SELECT username,password FROM users;", myConnection);
                SqlDataReader reader = userSELECTcom.ExecuteReader();

                    //verify login
                    while (reader.Read())
                    {
                        CompareUsername = reader["username"].ToString();
                        ComparePassword = reader["password"].ToString();
                        Log.Debug(ReceivedUsername + " against " + CompareUsername);
                        Log.Debug(ReceivedPassword + " against " + ComparePassword);

                        if (CompareUsername == ReceivedUsername && ComparePassword == ReceivedPassword)
                        {
                            ValidLogin = true;
                            Log.Debug(ReceivedUsername + " has logged in successfully!!!");
                            myConnection.Close();//close sql conn
                            reader.Close();//close sqldatareader
                            return ValidLogin;
                        }

                        else if (CompareUsername != ReceivedUsername || ComparePassword != ReceivedPassword)
                        {
                            if (!reader.Read())
                            {
                                Log.Debug(ReceivedUsername + " has not logged in successfully with password: " + ReceivedPassword);
                                myConnection.Close();//close sql conn
                                reader.Close();//close sql data reader
                                return ValidLogin;
                            }
                        }
                    }
                    //end of verify sequence
            }

        }
        //logging any login request issues
        catch (Exception e)
        {
            Log.Debug(e);
        }
        return ValidLogin;

    }

我有一个日志程序设置，告诉我代码执行时发生的一切。这些界限：＆＃34; Log.Debug（ReceivedUsername +＆＃34;反对＆＃34; + CompareUsername）; Log.Debug（ReceivedPassword +＆＃34;反对＆＃34; + ComparePassword）; ＆＃34;

帮助我查看读者正在检查哪一行。我尝试了六行，每行有唯一的用户名和密码，结果基本上显示读者只检查第1,3和5行对用户的输入。因此，如果我尝试使用第2,4或6行的用户名和密码登录我的客户端，则会收到错误消息，说我的登录失败。任何人都可以解释为什么会这样吗？

Answer 1

在你没有找到登录时间的条件下，你有一个额外的Reader.Read()电话。这是跳到下一条记录，然后你的主循环Reader.Read()转到下一条记录。

但是，您不需要像这样循环。构建一个按用户名查找记录的查询。如果没有记录，则登录失败。如果有，请检查密码。

Answer 2

reader.Read()块内的if语句中有第二个while。这导致您的代码跳过记录。

Answer 3

else if (CompareUsername != ReceivedUsername || ComparePassword != ReceivedPassword)
{
if (!reader.Read())  //remove this condition it will skip the current loop                             
{
Log.Debug(ReceivedUsername + " has not logged in successfully with password: " + ReceivedPassword);
myConnection.Close();//close sql conn
reader.Close();//close sql data reader
return ValidLogin;
}
}

Answer 4

为了简单起见，您可以直接从数据库进行查询。

下面是检查db：

中是否存在收到的用户名和密码的示例代码

string sql = @"SELECT username,password FROM users 
             WHERE username=@username and password = @password";

SqlCommand userSELECTcom = new SqlCommand(sql, myConnection);
userSELECTcom.Parameters.AddWithValue(@username, ReceivedUsername);
userSELECTcom.Parameters.AddWithValue(@password, ReceivedPassword);

using(SqlDataReader reader = userSELECTcom.ExecuteReader())
{
   ValidLogin = reader.HasRows; 
}

SqlDataReader读取每隔一行？

4 个答案: