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");