How to select a number from random pool, then make so number can't be reselected

I'm basically trying to write a quiz as part of my classwork for computer programming, and I've ran into a spot of bother.

I want the questions to be selected from a random pool to discourage cheating, I could make it so that it randomly selects between the numbers of 1,8 but that can cause repeats in the questioning, which is something that I don't want.

Random random = new Random(); // We use this random object to choose random icons for the squares.

    List<int> Assignments = new List<int>()
    {

        1,2,3,4,5,6,7,8

    };

    Random RandomlyChooseNumbers = new Random();

    int AssignmentForQ1;
    int AssignmentForQ2;
    int AssignmentForQ3;
    int AssignmentForQ4;
    string CorrectAnswerA1;
    string CorrectAnswerA2;
    string CorrectAnswerA3;
    string CorrectAnswerA4;
    public double timePassed;
    public int calculatedScore;
    public int timeLeft;

    public frmQuizOneHardMode()
    {
        InitializeComponent();

        AssignQuestionToTextQ1();

    }

    private void AssignQuestionToTextQ1()
    {
        int randomNumber = RandomlyChooseNumbers.Next(Assignments.Count);

        AssignmentForQ1 = Assignments[randomNumber];

        Assignments.RemoveAt(randomNumber);

        AssignmentForQ2 = Assignments[randomNumber];

        Assignments.RemoveAt(randomNumber);

        AssignmentForQ3 = Assignments[randomNumber];

        Assignments.RemoveAt(randomNumber);

        AssignmentForQ4 = Assignments[randomNumber];

        Assignments.RemoveAt(randomNumber);
    }

But for some reason, the numbers are always the same, which means that AssignmentForQ1,Q2,Q3 and Q4 all show the exact same question, I have literally no idea what's going wrong here, can someone please help?