Extension Method - IEnumerable

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

namespace Shand.Extension
{
    public static partial class Extensions
    {
        public static bool IsEmpty<T>(this IEnumerable<T> source)
        {
            return source.Count() == 0;
        }

        public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
        {
            foreach (T item in source)
            {
                action(item);
            }
        }

        public static IEnumerable<T> Filter<T>(this IEnumerable<T> source, Func<T, bool> predicate)
        {
            return source.Where(predicate);
        }

        public static bool Contains<T>(this IEnumerable<T> source, Func<T, bool> predicate)
        {
            foreach (T item in source)
            {
                if (predicate(item))
                {
                    return true;
                }
            }
            return false;
        }
    }
}

これは切実にほしかった

List<int> ls = new List<int>();

if (ls.IsEmpty())
{
    Console.WriteLine("Empty");
}

わりと必須かも(ForEach)

List<int> ls = new List<int>{3, 1, 4};

ls.Select(x => x + 1).ForEach(Console.WriteLine);

Where を Filter と書きたかっただけ

List<int> ls = new List<int>{3, 1, 4};

foreach (int item in ls.Filter(x => x > 1))
{
    Console.WriteLine(item);
}

メソッドでの該当チェック

List<string> ls = new List<string> {"Akira", "Johnny", "Millia"};

if (ls.Contains(name => name == "Akira"))
{
    Console.WriteLine("Found");
}