Simplest way is to make a generic method which accepts a list and "shuffles" them: place all the questions (correct and incorrect) in a List and pass it to the method.
private List<T> Shuffle<T>(List<T> input)
{
List<T> results = new List<T>(input.Count);
List<T> working = new List<T>(input);
while (working.Count > 0)
{
int index = rand.Next(working.Count);
T random = working[index];
results.Add(random);
working.Remove(random);
}
return results;
}
private static Random rand = new Random();