Question

I am writing a method that will generate an unsigned int between 1 and 6 (boundaries included). The current method I have is below.

        private static Random random = new Random();
        ...
        private static uint GetRandomChannel()
        {
            return Convert.ToUInt32(random.Next(1, 6));
        }

I’ve run this method a thousand times and I get numbers 1 through 5 but never get 6. Why is this happening and how can I fix it?

Answer 1

The second parameter to random.Next() is an exclusive upper bound.

Parameters

minValue: The inclusive lower bound of the random number returned.

maxValue: The exclusive upper bound of the random number returned. maxValue must
be greater than or equal to minValue.

Return value

A 32-bit signed integer greater than or equal to minValue and less than maxValue; that is, the range of return values includes minValue but not maxValue. If minValue equals maxValue, minValue is returned.

This means that random.Next(1, 6) will only return values n in the range 1 <= n < 6.

So for your die rolling simulation you will need to use

random.Next(1, 7)

---

Note: The design of this API is odd. It has special case handling for minValue == maxValue which seems to needlessly complicate the API. If I had designed this API I would have made both parameters be inclusive limits. This would have resulted in a pleasing symmetry and would have allowed random numbers that cover the full range of int.