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

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

Answer 2

//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 3

Use this code instead:

private Random _random = new Random();

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

Answer 4

0 is the same as 0000.

241 is the same as 0241.

You could format the integer to a string with a leading zero.

Answer 5

Just one line code

int num = new Random().Next(1000, 9999);