bo/Common/qdr.fnd.core/Value/Extensions/EnumerableExt.cs

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

namespace Quadarax.Foundation.Core.Value.Extensions
{
    public static class EnumerableExt
    {
        private static Random _rand = new Random();
        private const string CS_MESSAGE_MUST_HAVE_ONE = "Collection must have at least one element.";
        private const string CS_MESSAGE_MUST_POSITIVE = "Must be positive number.";
        private const string CS_MESSAGE_MUST_SMALLER = "fromIndex must be smaller or equal to toIndex.";


        public static TElement GetRandom<TElement>(this IEnumerable<TElement> owner)
        {
            if (owner == null)
                throw new ArgumentNullException(nameof(owner));

            if (!owner.Any())
                throw new ArgumentOutOfRangeException(nameof(owner), CS_MESSAGE_MUST_HAVE_ONE);

            return GetRandom(owner, 0, owner.Count());
        }

        public static TElement GetRandom<TElement>(this IEnumerable<TElement> owner, int fromIndex, int toIndex = -1)
        {
            if (owner == null)
                throw new ArgumentNullException(nameof(owner));

            if (!owner.Any())
                throw new ArgumentOutOfRangeException(nameof(owner), CS_MESSAGE_MUST_HAVE_ONE);

            if (toIndex == -1)
                toIndex = owner.Count() - 1;
            if (fromIndex<0)
                throw new ArgumentOutOfRangeException(nameof(fromIndex), CS_MESSAGE_MUST_POSITIVE);
            if (toIndex<0)
                throw new ArgumentOutOfRangeException(nameof(fromIndex), CS_MESSAGE_MUST_POSITIVE);
            if (fromIndex>toIndex)
                throw new ArgumentOutOfRangeException(nameof(fromIndex), CS_MESSAGE_MUST_SMALLER);

            var index = _rand.Next(fromIndex, toIndex);
            return owner.Skip(index).Take(1).First();


        }
    }
}