public void TestNullComparer_BuildComparer()
{
Random random = new Random();
// build a list of random dates
var dates = new List <DateTime>(getRandomDates(random));
// randomly choose which order to sort the components by
string[] propertyNames = { "Year", "Month", "Day", "Hour", "Minute", "Second" };
randomShuffle(propertyNames, random);
// build a comparer based on the order of the components
IComparer <DateTime> dateComparer = NullComparer <DateTime> .Default;
foreach (string propertyName in propertyNames)
{
string current = propertyName; // avoids non-local lambda problem
Func <DateTime, object> getter = (DateTime d) => typeof(DateTime).GetProperty(current).GetValue(d, null);
bool ascending = random.Next() % 2 == 0;
if (ascending)
{
dateComparer = dateComparer.ThenBy(getter);
}
else
{
dateComparer = dateComparer.ThenByDescending(getter);
}
}
// now we can sort the dates accordingly
dates.Sort(dateComparer);
}
public static IComparer <T> Defer <T>(this IComparer <T> first, Predicate <T> test) => first.ThenByDescending(new TestComparer <T>(test));
