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

Expanding on the answer from brij but with 0000 to 9999 rather than 1000 to 9999

string formatting = "0000"; //Will pad out to four digits if under 1000   
int _min = 0;
int _max = 9999;
Random randomNumber = new Random();
var randomNumberString = randomNumber.Next(_min, _max).ToString(formatting);

or if you want to minimalize lines:

Random randomNumber = new Random();
var randomNumberString = randomNumber.Next(0, 9999).ToString("0000");

Answer 2

Use this code instead:

private Random _random = new Random();

public string GenerateRandomNo()
{
    return _random.Next(0, 9999).ToString("D4");
}

Answer 3

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

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

Answer 4

//Generate RandomNo
public int GenerateRandomNo()
{
    int _min = 1000;
    int _max = 9999;
    Random _rdm = new Random();
    return _rdm.Next(_min, _max);
}

you need a 4 digit code, start with 1000

Answer 5

use: int _min = 1000;

or use leading 0 in case if you want 0241

Answer 6

int NoDigits = 4;
Random rnd = new Random();
textBox2.Text = rnd.Next((int)Math.Pow(10, (NoDigits - 1)), (int)Math.Pow(10, NoDigits) -1).ToString();