List<int> fulNumList = new List<int>();
List<int> pickedNumber = new List<int>();
void Start(){
for (int i = 1; i < 50; i++) {
fulNumList.Add(i);
}
//now all possible numbers are in fulNumList
for (int i = 0; i < 3; i++) {
int indexNum = Random.Range(0,fulNumList.Count);
//get a random index number form 0-49
int randomNum = fulNumList [indexNum];
pickedNumber.Add(randomNum);
//store randomNumber into pikedNumber list
fulNumList.RemoveAt(indexNum);
//remove the number that stored in pickedNumber from fulNumList for avoiding repeat numbers
}
pickedNumber.Sort ();
foreach (int result in pickedNumber){
Debug.Log (result);
}
}