GroupedEnumerable.cs

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using System.Collections;
using System.Collections.Generic;
 
namespace System.Linq;
 
internal sealed class GroupedEnumerable<TSource, TKey, TElement> : IIListProvider<IGrouping<TKey, TElement>>, IEnumerable<IGrouping<TKey, TElement>>, IEnumerable
{
    private readonly IEnumerable<TSource> _source;
 
    private readonly Func<TSource, TKey> _keySelector;
 
    private readonly Func<TSource, TElement> _elementSelector;
 
    private readonly IEqualityComparer<TKey> _comparer;
 
    public IGrouping<TKey, TElement>[] ToArray()
    {
        IIListProvider<IGrouping<TKey, TElement>> iIListProvider = Lookup<TKey, TElement>.Create(_source, _keySelector, _elementSelector, _comparer);
        return iIListProvider.ToArray();
    }
 
    public List<IGrouping<TKey, TElement>> ToList()
    {
        IIListProvider<IGrouping<TKey, TElement>> iIListProvider = Lookup<TKey, TElement>.Create(_source, _keySelector, _elementSelector, _comparer);
        return iIListProvider.ToList();
    }
 
    public int GetCount(bool onlyIfCheap)
    {
        if (!onlyIfCheap)
        {
            return Lookup<TKey, TElement>.Create(_source, _keySelector, _elementSelector, _comparer).Count;
        }
        return -1;
    }
 
    public GroupedEnumerable(IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer)
    {
        if (source == null)
        {
            ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
        }
        if (keySelector == null)
        {
            ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keySelector);
        }
        if (elementSelector == null)
        {
            ThrowHelper.ThrowArgumentNullException(ExceptionArgument.elementSelector);
        }
        _source = source;
        _keySelector = keySelector;
        _elementSelector = elementSelector;
        _comparer = comparer;
    }
 
    public IEnumerator<IGrouping<TKey, TElement>> GetEnumerator()
    {
        return Lookup<TKey, TElement>.Create(_source, _keySelector, _elementSelector, _comparer).GetEnumerator();
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}
internal sealed class GroupedEnumerable<TSource, TKey> : IIListProvider<IGrouping<TKey, TSource>>, IEnumerable<IGrouping<TKey, TSource>>, IEnumerable
{
    private readonly IEnumerable<TSource> _source;
 
    private readonly Func<TSource, TKey> _keySelector;
 
    private readonly IEqualityComparer<TKey> _comparer;
 
    public IGrouping<TKey, TSource>[] ToArray()
    {
        IIListProvider<IGrouping<TKey, TSource>> iIListProvider = Lookup<TKey, TSource>.Create(_source, _keySelector, _comparer);
        return iIListProvider.ToArray();
    }
 
    public List<IGrouping<TKey, TSource>> ToList()
    {
        IIListProvider<IGrouping<TKey, TSource>> iIListProvider = Lookup<TKey, TSource>.Create(_source, _keySelector, _comparer);
        return iIListProvider.ToList();
    }
 
    public int GetCount(bool onlyIfCheap)
    {
        if (!onlyIfCheap)
        {
            return Lookup<TKey, TSource>.Create(_source, _keySelector, _comparer).Count;
        }
        return -1;
    }
 
    public GroupedEnumerable(IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
    {
        if (source == null)
        {
            ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
        }
        if (keySelector == null)
        {
            ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keySelector);
        }
        _source = source;
        _keySelector = keySelector;
        _comparer = comparer;
    }
 
    public IEnumerator<IGrouping<TKey, TSource>> GetEnumerator()
    {
        return Lookup<TKey, TSource>.Create(_source, _keySelector, _comparer).GetEnumerator();
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}