/// <summary>
/// Composes a comparer that performs subsequent ordering using the key comparison.
/// </summary>
/// <typeparam name="T">The type being compared.</typeparam>
/// <typeparam name="TKey">The type of the key.</typeparam>
/// <param name="baseComparer">The comparer to extend.</param>
/// <param name="keySelector">The key of the type to use for comparison.</param>
/// <returns>A comparer that performs comparisons using both comparison operations.</returns>
/// <exception cref="System.ArgumentNullException">The base comparer is null.</exception>
/// <exception cref="System.ArgumentNullException">The key selector is null.</exception>
public static IComparer <T> ThenBy <T, TKey>(this IComparer <T> baseComparer, Func <T, TKey> keySelector)
{
if (baseComparer is null)
{
throw new ArgumentNullException(nameof(baseComparer));
}
var comparer = KeyComparer <T> .OrderBy(keySelector);
var compoundComparer = CompoundComparer <T> .GetComparer(baseComparer, comparer);
return(compoundComparer);
}
/// <summary>
/// Composes a comparer that performs subsequent ordering using the key comparison.
/// </summary>
/// <typeparam name="T">The type being compared.</typeparam>
/// <typeparam name="TKey">The type of the key.</typeparam>
/// <param name="baseComparer">The comparer to extend.</param>
/// <param name="keySelector">The key of the type to use for comparison.</param>
/// <param name="keyComparer">The comparer to use to compare the keys.</param>
/// <returns>A comparer that performs comparisons using both comparison operations.</returns>
/// <exception cref="System.ArgumentNullException">The base comparer is null.</exception>
/// <exception cref="System.ArgumentNullException">The key selector is null.</exception>
/// <exception cref="System.ArgumentNullException">The key comparison delegate is null.</exception>
public static IComparer <T> ThenBy <T, TKey>(this IComparer <T> baseComparer, Func <T, TKey> keySelector, IComparer <TKey> keyComparer)
{
if (baseComparer == null)
{
throw new ArgumentNullException("baseComparer");
}
IComparer <T> comparer = KeyComparer <T> .OrderBy(keySelector, keyComparer);
IComparer <T> compoundComparer = CompoundComparer <T> .GetComparer(baseComparer, comparer);
return(compoundComparer);
}