使用for循环将数据库记录存储到数组中 C＃

Question

I am creating an online test software using C# winforms and SQL Server. Now I have two tables (SQL server) one of is a question , and one is the question_answers . I am inserting the questions and their answers from the database to the array. I have the code something like this.

public dbtest()
        {
            sqlconnection = new SqlConnection(ConnectionString);
            Query =
                "SELECT questions.id as qid, questions.question as qq FROM dbo.questions; ";
            sqlcommand = new SqlCommand(Query, sqlconnection);
            sqlconnection.Open();
            SqlDataReader sdr = sqlcommand.ExecuteReader();

            while (sdr.Read())
            {
                int quiz_id;
                bool quiz_id1 = Int32.TryParse(sdr["qid"].ToString(), out quiz_id);

                sqlconnection = new SqlConnection(ConnectionString);
                Query =
                "SELECT id, question_id, answer, is_correct FROM dbo.question_answers WHERE question_id = " + quiz_id + "  ; ";
                sqlcommand = new SqlCommand(Query, sqlconnection);
                sqlconnection.Open();
                SqlDataReader answr = sqlcommand.ExecuteReader();

                while (answr.Read())
                {
                    questions[quiz_id, 0] = sdr["qq"].ToString();
                    for (int ii = 1; ii < 5; ii++)
                    {
                        questions[quiz_id, ii] = answr["answer"].ToString();
                    }
                }
            }
        }

I need an array to do like this.

            questions[0, 0] = "The 2006 World Cup Football Tournament held in";
            questions[0, 1] = "France";
            questions[0, 2] = "China";
            questions[0, 3] = "*Germany";
            questions[0, 4] = "Brazil";
            //
            questions[1, 0] = "The 'Black flag' signifies";
            questions[1, 1] = "revolution/danger";
            questions[1, 2] = "*protest";
            questions[1, 3] = "truce";
            questions[1, 4] = "peace";
            //
            questions[2, 0] = "Robert Koch worked on";
            questions[2, 1] = "*tuberculosis";
            questions[2, 2] = "cholera";
            questions[2, 3] = "malaria";
            questions[2, 4] = "diabetes";

But when I use for loop , I get the same answer records like this.

            questions[0, 0] = "The 2006 World Cup Football Tournament held in";
            questions[0, 1] = "France";
            questions[0, 2] = "France";
            questions[0, 3] = "France";
            questions[0, 4] = "France";
            //

I am new in C# winfroms programming. And I can not get better algorithm. So I have two questions. The first one: How can I fix this code's problem?

                {
                    questions[quiz_id, 0] = sdr["qq"].ToString();
                    for (int ii = 1; ii < 5; ii++)
                    {
                        questions[quiz_id, ii] = answr["answer"].ToString();
                    }
                }

The second: Are there other optimally solutions to get questions and their answers from database? Excuse me if I can not explain. Thanks for answers!

Answer 1

the following code :

for (int ii = 1; ii < 5; ii++)
{
    questions[quiz_id, ii] = answr["answer"].ToString();
}

will set the same answer in the sub array questions [0, X] with X between 1 and 4.
And then another answer in the sub array questions [1, X] with X between 1 and 4.
And then another answer in the sub array questions [2, X] with X between 1 and 4.

You need to get rid of that unnecessary loop.

public dbtest(){
        sqlconnection = new SqlConnection(ConnectionString);
        Query =
            "SELECT questions.id as qid, questions.question as qq FROM dbo.questions; ";
        sqlcommand = new SqlCommand(Query, sqlconnection);
        sqlconnection.Open();
        SqlDataReader sdr = sqlcommand.ExecuteReader();

        while (sdr.Read())
        {
            int quiz_id;
            bool quiz_id1 = Int32.TryParse(sdr["qid"].ToString(), out quiz_id);

            sqlconnection = new SqlConnection(ConnectionString);
            Query =
            "SELECT id, question_id, answer, is_correct FROM dbo.question_answers WHERE question_id = " + quiz_id + "  ; ";
            sqlcommand = new SqlCommand(Query, sqlconnection);
            sqlconnection.Open();
            SqlDataReader answr = sqlcommand.ExecuteReader();
            questions[quiz_id, 0] = sdr["qq"].ToString();
            var ii = 1;
            while (answr.Read())
            {
                questions[quiz_id, ii] = answr["answer"].ToString();
                ii++;
            }
        }
    }

You could use SQL join to map question and answer and just transform the result set into an array of some sort.