C# Filter extensions

FilterExtentions.cs

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

namespace Utils.Extensions
{
    public static class FilterExtensions
    {
        /// <summary>
        /// Remove null values from the collection.
        /// </summary>
        /// <typeparam name="TSource">The type of the source.</typeparam>
        /// <param name="items">The items.</param>
        /// <returns></returns>
        public static IList<TSource> Filter<TSource>(this IList<TSource> items) where TSource : class
        {
            return FilterInternal(items, item => item != null).ToList();
        }

        /// <summary>
        /// Remove null values from the collection.
        /// </summary>
        /// <typeparam name="TSource">The type of the source.</typeparam>
        /// <param name="items">The items.</param>
        /// <returns></returns>
        public static IEnumerable<TSource> Filter<TSource>(this IEnumerable<TSource> items) where TSource : class
        {
            return FilterInternal(items, item => item != null);
        }

        /// <summary>
        /// Remove items from the collection that dosen't match the given predicate. 
        /// </summary>
        /// <typeparam name="TSource">The type of the source.</typeparam>
        /// <param name="items">The items.</param>
        /// <param name="predicate">The predicate.</param>
        /// <returns></returns>
        public static IList<TSource> Filter<TSource>(this IList<TSource> items, Func<TSource, bool> predicate) where TSource : class
        {
            return FilterInternal(items, predicate).ToList();
        }

        /// <summary>
        /// Remove items from the collection that dosen't match the given predicate. 
        /// </summary>
        /// <typeparam name="TSource">The type of the source.</typeparam>
        /// <param name="items">The items.</param>
        /// <param name="predicate">The predicate.</param>
        /// <returns></returns>
        public static IEnumerable<TSource> Filter<TSource>(this IEnumerable<TSource> items, Func<TSource, bool> predicate) where TSource : class
        {
            return FilterInternal(items, predicate).ToList();
        }

        private static IEnumerable<TSource> FilterInternal<TSource>(IEnumerable<TSource> items, Func<TSource, bool> predicate) where TSource : class
        {
            if (items == null)
            {
                throw new ArgumentNullException("items");
            }
            
            if (predicate == null)
            {
                throw new ArgumentNullException("predicate");
            }
            
            return items.Where(predicate);
        }
    }
}