Unique 4 digit random number in C#

Question

I want to generate an unique 4 digit random number. This is the below code what I have tried:

Code for generating random number

//Ge         


        

Answer 1

I suggest to create new list and check if this list contains any of number

var IdList = new List();
do
{
    billId = random.Next(1, 9000);
} while (IdList.Contains(billId));
IdList.Add(billId);