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

Answer 2

use: int _min = 1000;

or use leading 0 in case if you want 0241

Answer 3

241 is a four digit number, if you use leading zeros: 0241.

Display the returned number with a format string like this:

String.Format("{0:0000}", n);

Answer 4

You can consider something like this.

int length = 4;
int number = 50;
string asString = number.ToString("D" + length);

The above code gives the result 0050.

Similarly you can try converting to string and verify.

Answer 5

Random generator = new Random();
string number = generator.Next(1, 10000).ToString("D4");

Answer 6

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");