ソースコード using System; using System.Collections.Generic; using System.Linq; public static class IEnumerableExtensions { private sealed class CommonSelector<T, TKey> : IEqualityComparer<T> { private Func<T, TKey> m_selector; public CommonSelector( Func<T, TKey> selector ) { m_selector = selector; } public bool Equals( T x, T y ) { return m_selector( x ).Equals( m_selector( y ) ); } public int GetHash
