Question

我正在迭代DayOfWeek Enum：

foreach (DayOfWeek day in Enum.GetValues(typeof(DayOfWeek)))
{
 // Add stuff to a list 
}

我的问题是，我希望我的枚举能够在星期一而不是星期天开始。

我试着这样做：

CultureInfo ci = Thread.CurrentThread.CurrentCulture;
ci.DateTimeFormat.FirstDayOfWeek = DayOfWeek.Monday;

但是foreach循环仍然在周日开始。

我该怎么做？

我的最后一个想法是将我的结果列表重新排序为我想要的日期顺序但这意味着更多的迭代。

谢谢！

Answer 1

这是不可能的，纯粹是因为设置文化不会改变DayOfWeek enum被定义为这样的事实：

public enum DayOfWeek {
    Sunday = 0,
    Monday = 1,
    Tuesday = 2,
    Wednesday = 3,
    Thursday = 4,
    Friday = 5,
    Saturday = 6,
}

但是，您可以跳过第一个条目并稍后添加..也许是这样：

foreach (DayOfWeek day in Enum.GetValues(typeof(DayOfWeek))
                              .OfType<DayOfWeek>()
                              .ToList()
                              .Skip(1)) {
    list.Add(day.ToString());
}
list.Add(DayOfWeek.Sunday.ToString());

Answer 2

对OrderBy的单次调用可以根据需要对其进行排序。无法将呼叫顺序更改为Enum.GetValues。

var daysOfWeek = Enum.GetValues(typeof(DayOfWeek))
    .OfType<DayOfWeek>()
    .OrderBy(day => day < DayOfWeek.Monday);

Answer 3

使用 for 循环和modulo（％）运算符：

DayOfWeek day;
for( int i = 0 ; i < 7 ; i++ )
{
    day = (DayOfWeek) ((i + 1) % 7);
    // Add stuff to a list
}

如果你想使用这个循环移动另一个枚举，你总是可以用这样初始化的变量替换数字7：

int length = Enum.GetValues(typeof(DayOfWeek)).Length;

你甚至可以编写一个移动任何枚举的方法，假设这个枚举具有 0,1，...，n 之间的所有值：

static IEnumerable<TEnum> Shift<TEnum>(int offset) where TEnum : struct
{
    int length = Enum.GetValues(typeof(TEnum)).Length;
    for( int i = 0 ; i < length ; i++ )
    {
        yield return (TEnum) (object) ((i + offset) % length);
    }
}

Answer 4

从自定义IComparer<DayOfWeek>开始：

public class DayOfWeekComparer : IComparer<DayOfWeek> {
    public int Compare(DayOfWeek x, DayOfWeek y) {
        return ModifyDayOfWeek(x).CompareTo(ModifyDayOfWeek(y));
    }

    private static int ModifyDayOfWeek(DayOfWeek x) {
        // redefine Sunday so it appears at the end of the ordering
        return x == DayOfWeek.Sunday ? 7 : (int)x;
    }
}

然后：

foreach(DayOfWeek day in Enum.GetValues(typeof(DayOfWeek))
                             .OfType<DayOfWeek>()
                             .OrderBy(x => x, new DayOfWeekComparer())) {
    // will see Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday
}

编辑添加：

实际上，即使太复杂了，也就像它一样漂亮。你为什么不把它放在

static IEnumerable<DayOfWeek> DaysOfWeek {
    get {
        yield return DayOfWeek.Monday;
        yield return DayOfWeek.Tuesday;
        yield return DayOfWeek.Wednesday;
        yield return DayOfWeek.Thursday;
        yield return DayOfWeek.Friday;
        yield return DayOfWeek.Saturday;
        yield return DayOfWeek.Sunday;
   }
}

某个地方，任何地方，只是完成它！ KISS！

Answer 5

Enum.GetValues返回按枚举常量的二进制值排序的元素（请参阅MSDN上的备注）。以这种方式定义DayOfWeek枚举：

public enum DayOfWeek
{
    Sunday = 0,
    Monday = 1,
    Tuesday = 2,
    Wednesday = 3
    Thursday = 4,
    Friday = 5,
    Saturday = 6,
}

如您所见，Monday定义为1，Sunday定义为0。因此，您无法强制Enum.GetValues方法在Monday之前返回Sunday。

Answer 6

为我工作：

class _MyAppState extends State<MyApp> {
  GlobalKey qrKey = GlobalKey();
  var qrText = "";
  QRViewController controller;
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      body: Column(
        children: [
          Expanded(
              flex: 5,
              child: QRView(
                key: qrKey,
                overlay: QrScannerOverlayShape(
                    borderRadius: 10,
                    borderColor: Colors.red,
                    borderLength: 30,
                    borderWidth: 10,
                    cutOutSize: 300),
                onQRViewCreated: _onQRViewCreate,
              )),
          Expanded(
            flex: 1,
            child: Center(
              child: InkWell(
                child: Text(
                  'Scan result: $qrText',
                ),
                onTap: () {
                  if (qrText.isNotEmpty) {
                    launch(qrText);
                  }
                },
              ),
            ),
          )
        ],
      ),
    );
  }

  @override
  void dispose() {
    controller?.dispose();
    super.dispose();
  }

  void _onQRViewCreate(QRViewController controller) {
    this.controller = controller;
    controller.scannedDataStream.listen((scanData) {
      setState(() {
        qrText = scanData;
      });
    });
  }
}

通过DayOfWeek枚举的每个循环在星期一开始？

6 个答案: