A Random Weighted Picker in C#

RandomWeightedPicker.cs

// Author: Giovanni Costagliola <giovanni.costagliola@gmail.com>

using System;
using System.Collections.Generic;
using System.Linq;

namespace Utils
{
    /// <summary>
    /// Represent a Weighted Item.
    /// </summary>
    public interface IWeighted
    {
        /// <summary>
        /// A positive weight. It's up to the implementer ensure this requirement
        /// </summary>
        int Weight { get; }
    }

    /// <summary>
    /// Pick up an element reflecting its weight.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class RandomWeightedPicker<T> where T:IWeighted
    {
        private readonly IEnumerable<T> items;
        private readonly int totalWeight;
        private Random random = new Random();

        /// <summary>
        /// Initiliaze the structure. O(1) or O(n) depending by the options, default O(n).
        /// </summary>
        /// <param name="items">The items</param>
        /// <param name="checkWeights">If <c>true</c> will check that the weights are positive. O(N)</param>
        /// <param name="shallowCopy">If <c>true</c> will copy the original collection structure (not the items). Keep in mind that items lifecycle is impacted.</param>
        public RandomWeightedPicker(IEnumerable<T> items, bool checkWeights = true, bool shallowCopy = true)
        {
            if (items == null) throw new ArgumentNullException("items");
            if (!items.Any()) throw new ArgumentException("items cannot be empty");
            if (shallowCopy)
                this.items = new List<T>(items);
            else
                this.items = items;
            if (checkWeights && this.items.Any(i => i.Weight <= 0))
            {
                throw new ArgumentException("There exists some items with a non positive weight");
            }
            totalWeight = this.items.Sum(i => i.Weight);
        }
        /// <summary>
        /// Pick a random item based on its chance. O(n)
        /// </summary>
        /// <param name="defaultValue">The value returned in case the element has not been found</param>
        /// <returns></returns>
        public T PickAnItem()
        {
            int rnd = random.Next(totalWeight);
            return items.First(i => (rnd -= i.Weight) < 0);
        }

        /// <summary>
        /// Resets the internal random generator. O(1)
        /// </summary>
        /// <param name="seed"></param>
        public void ResetRandomGenerator(int? seed)
        {
            random = seed.HasValue ? new Random(seed.Value) : new Random();
        }
    }
}