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

//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