Random XML Questions Using Fisher-Yates Shuffle

I am making a Quiz/Trivia Game and have questions stored in XML file and it gets a random question. Everything works fine, but I want to stay random but not show the same question until every question has been shown.

 public struct Question {
     public string questionText;
     public string answerA;
     public string answerB;
     public string answerC;
     public string answerD;
     public int correctAnswerID;
 }
 
 [XmlRoot("QuestionsRoot")]
    public class QuestionData {
 [XmlArray("Questions")]
 [XmlArrayItem("Question")]
 public List<Question>questions = new List<Question>();
 
 public static QuestionData LoadFromText(string text) {
     try {
         XmlSerializer serializer = new XmlSerializer(typeof(QuestionData));            
         return serializer.Deserialize(new StringReader(text)) as QuestionData;
     } catch (Exception e) {
         UnityEngine.Debug.LogError("Exception loading question data: " + e);
         return null;
     }
 }

}

And I use this to get a random question:

     questionData = QuestionData.LoadFromText(questionDataXMLFile.text)

     q = Random.Range(0, questionData.questions.Count);
     currentQuestion = questionData.questions[q];