WeighedRandom

  public class WeighedRandom
    {
        private Random ran = new Random();
        private List<int[]> _Weight_Range = new List<int[]>();
        /// <summary>
        /// Add an array with 2 numbers
        /// [1] MaxValue for random number
        /// [2] Weight
        /// { maxval, weight }
        /// </summary>
        public List<int[]> Weight_Range
        {
            get { return _Weight_Range; }
            set { _Weight_Range = value; }
        }

        private int[] WeightedNums = new int[] { };
        private int TotalNums = 0;

        public void CreateRandomArray()
        {
            // use all the weights and total them to make the array total
            for (int t = 0; t < Weight_Range.Count; t++)
                TotalNums += Weight_Range[t][1];

            // make the array
            WeightedNums = new int[TotalNums];

            // Populate array with 0s
            for (int i = 0; i < TotalNums; i++)
                WeightedNums[i] = 0;

            int count = 0;

            for (int i = 0; i < Weight_Range.Count; i++)
            {
                for (int j = 0; j < Weight_Range[i][1]; j++)
                {
                    WeightedNums[count++] = Weight_Range[i][0];
                }
            }
        }

        public int ReturnRandomValue()
        {
            return ran.Next(1,WeightedNums[ran.Next(0,TotalNums)]);
        }
    }