How to get List data from class to Form

Question

How can I get var finalQuestions from class Question to my GroupExmStart Form in this string QuestionSet = "";? How I can get it in Form and what conversions do I need to do to store it as string? I want to store it as string because this QuestionSet I have to pass here: int z = Quiz(QuestionSet);,how could I do this? Is their a better way with which I can achieve this?

GroupExmStart Form

public partial class GroupExmStart : Form
{
    string QuestionSet = "";
    public GroupExmStart(string GroupName, string DurationID)
    {
        InitializeComponent();

        this.GrpID=GroupName;
        TopiID=db.GetTopicIDForGroup(GrpID);

        Question qsn = new Question();           

        string[] conf = db.GetConfiguration(Convert.ToInt16(DurationID)).Split('|');
        qsn.Foo(TopiID, conf);
        int z = Quiz(QuestionSet);
    }

    int Quiz(string data)
    {
        string[] words = data.Split('$');
        randomQsn = new string[totQsn + 1];
        QAndA = new string[words.Length + 1];
        for (int i = 0; i < words.Length; i++)
        {
            QAndA[i] = words[i];
        }

        return 0;
    }

    private void Question(string id, string Q, string OP1, string OP2, string OP3, string OP4)
    {
        label5.Text = Q;

        radioButton12.Text = OP4;
        radioButton11.Text = OP4;
        radioButton10.Text = OP4;
        radioButton9.Text = OP4;
    }
}

Class Question

public class Question
{
    public string Id { get; set; }
    public string Text { get; set; }

    public string Option1 { get; set; }
    public string Option2 { get; set; }
    public string Option3 { get; set; }
    public string Option4 { get; set; }

    public string AnswerOption { get; set; }
    public int Marks { get; set; }
    Random _random = new Random();

    public IEnumerable<Question> GetQuestions(string topicId, int marks)
    {            
        string sql = "select QID,Question,Opt1,Opt2,Opt3,Opt4,AnsOp,Marks from Questions where TopicID IN(" +
                         topicId + ") and Marks=" + marks.ToString();
        var cmd = new OleDbCommand(sql,acccon);
        var rs = cmd.ExecuteReader();

        if (rs != null)
        {
            while (rs.Read())
            {
                yield return
                new Question
                {
                    Id = rs[0].ToString(),
                    Text = rs[1].ToString(),
                    Option1 = rs[2].ToString(),
                    Option2 = rs[3].ToString(),
                    Option3 = rs[4].ToString(),
                    Option4 = rs[5].ToString(),
                    AnswerOption = rs[6].ToString(),
                    Marks = marks
                 };
             }
        }
    }

    public void Foo(string TopicId,string[] conf)
    {
        var totQsn = Convert.ToInt16(conf[0]); 
        var mark1qsn = Convert.ToInt16(conf[3]); //this variable contains number of question to be display of mark 1
        var mark2qsn = Convert.ToInt16(conf[4]);
        var mark3qsn = Convert.ToInt16(conf[5]);
        var mark4qsn = Convert.ToInt16(conf[6]);

        var mark1questionSet = GetQuestions(TopicId, 1).ToList();
        var mark2questionSet = GetQuestions(TopicId, 2).ToList();

        //this finalQuestions I want to access in my Form               
        var finalQuestions = new List<Question>();

        for (int i = 0; i < mark1qsn; i++)
        {
            var setIndex = _random.Next(mark1questionSet.Count);
            finalQuestions.Add(mark1questionSet[setIndex]);
            mark1questionSet.RemoveAt(setIndex);
        }

        for (int i = 0; i < mark2qsn; i++)
        {
            var setIndex = _random.Next(mark2questionSet.Count);
            finalQuestions.Add(mark2questionSet[setIndex]);
            mark2questionSet.RemoveAt(setIndex);
        }            
    }        
}    

Answer 1

Have method Foo return the final questions variable...

public List<Question> Foo(string TopicId, string[] conf)
{
    // do all the same stuff...
    return finalQuestions;
}

Then, in your GroupExmStart method do the following...

Question qsn = new Question();
string[] conf = db.GetConfiguration(Convert.ToInt16(DurationID)).Split('|');
QuestionSet = string.Join(",", qsn.Foo(TopiID, conf));
int z = Quiz(QuestionSet);

Edit per comment #1

A better way, IMO, would be to not join them to begin with; and just pass the list of questions into the Quiz method directly. So you would have to alter the Quiz method to take a list of Questions like:

int Quiz(List<Question> questions)

And then remove the string.Join from above.

Question qsn = new Question();
string[] conf = db.GetConfiguration(Convert.ToInt16(DurationID)).Split('|');
var questions = qsn.Foo(TopiID, conf);
int z = Quiz(questions);

Edit per comment #3

private void Question(Question q)
{
    label5.Text = string.Format("{0} {1}", q.Id, q.Text);

    radioButton12.Text = q.Option1;
    radioButton11.Text = q.Option2;
    radioButton10.Text = q.Option3;
    radioButton9.Text = q.Option4;
}