AnyAll.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

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

namespace System.Linq
{
    public static partial class Enumerable
    {
        public static bool Any<TSource>(this IEnumerable<TSource> source)
        {
            if (source == null)
            {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
            }

            if (source is ICollection<TSource> collectionoft)
            {
                return collectionoft.Count != 0;
            }
            else if (source is IIListProvider<TSource> listProv)
            {
                // Note that this check differs from the corresponding check in
                // Count (whereas otherwise this method parallels it).  If the count
                // can't be retrieved cheaply, that likely means we'd need to iterate
                // through the entire sequence in order to get the count, and in that
                // case, we'll generally be better off falling through to the logic
                // below that only enumerates at most a single element.
                int count = listProv.GetCount(onlyIfCheap: true);
                if (count >= 0)
                {
                    return count != 0;
                }
            }
            else if (source is ICollection collection)
            {
                return collection.Count != 0;
            }

            using (IEnumerator<TSource> e = source.GetEnumerator())
            {
                return e.MoveNext();
            }
        }

        public static bool Any<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
        {
            if (source == null)
            {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
            }

            if (predicate == null)
            {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.predicate);
            }

            foreach (TSource element in source)
            {
                if (predicate(element))
                {
                    return true;
                }
            }

            return false;
        }

        public static bool All<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
        {
            if (source == null)
            {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
            }

            if (predicate == null)
            {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.predicate);
            }

            foreach (TSource element in source)
            {
                if (!predicate(element))
                {
                    return false;
                }
            }

            return true;
        }
    }
}