C# SQLite and SQL commands Specified cast not valid

Question

I'm playing around with SQlite and sql commands. I'm trying to make a quizz program and I have a loop, that reads the questions and answers from my database and adds them to a list. I also have a bool that defines if the answer picked from the database is right or wrong.

My problem is that all this works fine the first time my loop executes the code and adds the true and false to my array of bools, but the 2'nd time my loop executes it throws the exception: SPECIFIED CAST NOT VALID. The method that fails looks like this: I made a comment where the code fails:

    public void GetQuestion(int categoryRef)
    {
        Console.Clear();

        int arrayIndex = 0;

        int qListIndex = 0;

        int idListIndex = 0;

        List<string> qList = new List<string>();

        List<int> idList = new List<int>();

        int ansNr = 1;

        bool[] isTrue = new bool[3];


        SQLiteDataReader sqReader;

        SQLiteCommand sqCommand = new SQLiteCommand(sqConnection);

        try
        {
            sqCommand.CommandText = "SELECT Question, ID FROM Questions WHERE CategoryRef=" + categoryRef.ToString();
            sqCommand.Connection.Open();
            sqReader = sqCommand.ExecuteReader();
            foreach (var item in sqReader)
            {
                qList.Add(sqReader.GetString(0));
                idList.Add(sqReader.GetInt32(1));
            }
            sqReader.Close();
        }
        finally
        {
            sqConnection.Close();    
        }

        for (int i = 0; i < qList.Count; i++)
        {   
            try
            {
                sqCommand.CommandText = "SELECT Answer FROM Answers WHERE QuestionRef=" + idList[idListIndex].ToString();
                sqConnection.Open();
                sqReader = sqCommand.ExecuteReader();
                Console.WriteLine(qList[qListIndex]);
                foreach (var answer in sqReader)
                {
                    Console.WriteLine(ansNr + ":" + sqReader.GetString(0));

                    ansNr++;
                }
                sqReader.Close();
            }
            finally
            {
                sqConnection.Close();
            }

            try
            {   
                //THIS CODE FAILS 2'nd TIME IT LOOPS THROUGH
                sqCommand.CommandText = "SELECT IsTrue FROM Answers WHERE QuestionRef=" + idList[idListIndex].ToString();
                sqConnection.Open();
                sqReader = sqCommand.ExecuteReader();
                foreach (var item in sqReader)
                {

                    isTrue[arrayIndex] = sqReader.GetBoolean(0); //<-- Specified cast is not valid.
                    arrayIndex++;


                }
                sqReader.Close();
            }
            finally
            {

                sqConnection.Close();
            }

            string input = Console.ReadLine();
            int number = Convert.ToInt32(input);

            switch (number)
            {
                case 1:
                    if (isTrue[0] == true)
                    {
                        Console.WriteLine("Correct");
                    }
                    if (isTrue[0] == false)
                    {
                        Console.WriteLine("False");
                    }
                    break;

                case 2:
                    if (isTrue[1] == true)
                    {
                        Console.WriteLine("Correct");
                    }
                    if (isTrue[1] == false)
                    {
                        Console.WriteLine("False");
                    }
                    break;

                case 3:
                    if (isTrue[2] == true)
                    {
                        Console.WriteLine("Correct");
                    }
                    if (isTrue[2] == false)
                    {
                        Console.WriteLine("False");
                    }
                    break;
            }
            Console.ReadLine();
            idListIndex++;
            qListIndex++;
            arrayIndex = 0;
            ansNr = 1;
        }
    }

Answer 1

Mostly likely, that you read DbNull from database, which cannot be cast to bool.