/// <summary>
/// Combines <see cref="MoreEnumerable.OrderBy{T, TKey}(IEnumerable{T}, Func{T, TKey}, IComparer{TKey}, OrderByDirection)"/>,
/// where each element is its key, and <see cref="Enumerable.Take{TSource}"/>
/// in a single operation.
/// Additional parameters specify how the elements compare to each other and
/// the direction of the sort.
/// </summary>
/// <typeparam name="T">Type of elements in the sequence.</typeparam>
/// <param name="source">The source sequence.</param>
/// <param name="count">Number of (maximum) elements to return.</param>
/// <param name="comparer">A <see cref="IComparer{T}"/> to compare elements.</param>
/// <param name="direction">The direction in which to sort the elements</param>
/// <returns>A sequence containing at most top <paramref name="count"/>
/// elements from source, in the specified order.</returns>
/// <remarks>
/// This operator uses deferred execution and streams it results.
/// </remarks>
public static IEnumerable <T> PartialSort <T>(this IEnumerable <T> source,
int count, IComparer <T> comparer, OrderByDirection direction)
{
comparer = comparer ?? Comparer <T> .Default;
if (direction == OrderByDirection.Descending)
{
comparer = new ReverseComparer <T>(comparer);
}
return(source.PartialSort(count, comparer));
}
/// <summary>
/// Combines <see cref="MoreEnumerable.OrderBy{T, TKey}(IEnumerable{T}, Func{T, TKey}, OrderByDirection)"/>,
/// and <see cref="Enumerable.Take{TSource}"/> in a single operation.
/// Additional parameters specify how the elements compare to each other and
/// the direction of the sort.
/// </summary>
/// <typeparam name="TSource">Type of elements in the sequence.</typeparam>
/// <typeparam name="TKey">Type of keys.</typeparam>
/// <param name="source">The source sequence.</param>
/// <param name="keySelector">A function to extract a key from an element.</param>
/// <param name="count">Number of (maximum) elements to return.</param>
/// <param name="comparer">A <see cref="IComparer{T}"/> to compare elements.</param>
/// <param name="direction">The direction in which to sort the elements</param>
/// <returns>A sequence containing at most top <paramref name="count"/>
/// elements from source, in the specified order of their keys.</returns>
/// <remarks>
/// This operator uses deferred execution and streams it results.
/// </remarks>
public static IEnumerable <TSource> PartialSortBy <TSource, TKey>(
this IEnumerable <TSource> source, int count,
Func <TSource, TKey> keySelector,
IComparer <TKey> comparer,
OrderByDirection direction)
{
comparer = comparer ?? Comparer <TKey> .Default;
if (direction == OrderByDirection.Descending)
{
comparer = new ReverseComparer <TKey>(comparer);
}
return(source.PartialSortBy(count, keySelector, comparer));
}
