Can't generate random number

I'm trying to generate random numbers in a loop. I make an instance of the Random class before the loop starts, but it is inaccessible. The error i get is:

'System.Random.Sample()' is inaccessible due to its protection level

My code is:

Random random = new Random();
   while (ready == false)
   {
       double h = random.Sample();
   //Lots of things done here
   }

What's wrong?