Samples the collection using a uniform distribution, do not repeat elements.

Sample.cs

    /// <summary>
    /// SampleService
    /// </summary>
    public class SampleService
    {
        private readonly Random _random;

        /// <summary>
        /// Initializes a new instance of the <see cref="SampleService"/> class.
        /// </summary>
        /// <param name="seed">The seed.</param>
        public SampleService(int seed = 0)
        {
            _random = new Random(seed == 0 ? (int)DateTime.Now.Ticks : seed);
        }

        /// <summary>
        /// Samples the specified universe.
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="universe">The universe.</param>
        /// <param name="sampleSize">Size of the sample.</param>
        /// <returns></returns>
        /// <exception cref="System.ArgumentException">sample size is larger than collection</exception>
        public T[] Sample<T>(IEnumerable<T> universe, int sampleSize)
        {
            var tmp = universe.ToArray();

            if (sampleSize > tmp.Length)
            {
                throw new ArgumentException("sample size is larger than collection");
            }

            var tmpReturn = new T[sampleSize];
            var usedIndicies = new HashSet<int>();

            for (var i = 0; i < sampleSize; i++)
            {
                int sampleIndex;

                do { sampleIndex = _random.Next(0, tmp.Length); }
                while (!usedIndicies.Add(sampleIndex));

                tmpReturn[i] = tmp[sampleIndex];
            }

            return tmpReturn;
        }
    }