要标记一个lambda异步，在它的参数列表前加上async： // Add a command to delete the current Group contextMenu.Commands.Add(new UICommand("Delete this Group", async (contextMenuCmd) => { SQLiteUtils slu = new SQLiteUtils(); await slu.DeleteGroupAsync(groupName); })); ... 展开详请

def blank_fn(*args, **kwargs): pass 然而，我认为更多的方法是： def perform_task(callback=None): print 'doing stuff' if callback is not None: callback('x', 'y', z='z') def do_nothing(*args, **kwargs): pass def do_something(arg, callback=do_nothing): a = 1 + 2 callback('z', z='z') def do_something_else(arg, callback=None): a = 1 + 2 if callback is not None: callback('z', z='z') %timeit do_something(3) 1000000 loops, best of 3: 644 ns per loop %timeit do_something_else(3) 1000000 loops, best of 3: 292 ns per loop... 展开详请

myCollection.GroupBy(x => x.Id) .Select(y => new { Id = y.Key, Quantity = y.Sum(x => x.Quantity) });... 展开详请

是否需要列表进行排序，或只是列表内容的有序序列？后者更容易： var peopleInOrder = people.OrderBy(person => person.LastName); 要排序，你需要一个IComparer<Person>或一个Comparison<Person>。为此，您可能希望ProjectionComparer在MiscUtil中考虑。... 展开详请