System.Linq.Lookup<TKey, TElement>
public class Lookup<TKey, TElement> : IEnumerable<IGrouping<TKey, TElement>>, IEnumerable, ILookup<TKey, TElement>
namespace System.Linq
{
public class Lookup<TKey, TElement> : IEnumerable<IGrouping<TKey, TElement>>, IEnumerable, ILookup<TKey, TElement>
{
public int Count { get; }
public IEnumerable<TElement> this[TKey key] { get; }
public IEnumerable<TResult> ApplyResultSelector<TResult>(Func<TKey, IEnumerable<TElement>, TResult> resultSelector);
public bool Contains(TKey key);
public IEnumerator<IGrouping<TKey, TElement>> GetEnumerator();
}
}