问题 三元问题

[豆镇]

这是设置可为空的DateTime的最佳方法吗？对于我有今天或明天的订购日期的对象，则设置一个日期，否则我需要将其设置为空。

    var order = new OrderSetup
                {
                    Customer = Customer,
                    Total = Total,
                    OrderDate = string.Compare(OrderStatus, "Today", StringComparison.OrdinalIgnoreCase) == 0 ?
                                     Dates.TodayOrderDate :
                                     string.Compare(OrderStatus, "Tomorrow", StringComparison.OrdinalIgnoreCase) == 0 ?
                                     Dates.TommorrowOrderDate : (DateTime?)null //is this the best way where it seems like I have to set this as a nullable datetime.
                };

 

[金西尼]

If you're using C# 8.0 or later then you can use a switch expression. If I'm not mistaken, that would look like this:

OrderDate = OrderStatus switch
{
        "Today" => Dates.TodayOrderDate,
        "Tomorrow" => Dates.TomorrowOrderDate,
        _ => (DateTime?) null
}

 

[跳伞]

How do you force a case insensitive match with a switch?

 

[约翰·H]

How do you force a case insensitive match with a switch?

尽管看起来并不那么优雅，但这似乎可行：

var OrderDate = OrderStatus switch
{
    string _ when OrderStatus.Equals("Today", StringComparison.CurrentCultureIgnoreCase) => Dates.TodayOrderDate,
    string _ when OrderStatus.Equals("Tomorrow", StringComparison.CurrentCultureIgnoreCase) => Dates.TomorrowOrderDate,
    _ => (DateTime?)null
};

 

[金西尼]

How do you force a case insensitive match with a switch?

I kind of overlooked that part. Got all excited about using a switch expression, which I've never actually done before.

 

[金西尼]

尽管看起来并不那么优雅，但这似乎可行：

var OrderDate = OrderStatus switch
{
    string _ when OrderStatus.Equals("Today", StringComparison.CurrentCultureIgnoreCase) => Dates.TodayOrderDate,
    string _ when OrderStatus.Equals("Tomorrow", StringComparison.CurrentCultureIgnoreCase) => Dates.TomorrowOrderDate,
    _ => (DateTime?)null
};

我建议它可能比嵌套三元运算符还要优雅。

 

[跳伞]

The only way, I can think of to make things cleaner like in post #2 is to use switch Order status?.ToUpper(), and then put all the literal strings in caps, but that assumes that the input language is not Turkish and that the literal string to be compared does not contain an I.

 

[金西尼]

The only way, I can think of to make things cleaner like in post #2 is to use switch Order status?.ToUpper(), and then put all the literal strings in caps, but that assumes that the input language is not Turkish and that the literal string to be compared does not contain an I.

I can't help thinking that that OrderStatus should be an enum rather than a string 和 then case would be irrelevant. It depends what the possible values are but I would assume that only a specific set of values would be valid, in which case it absolutely should be an enum.

 

[跳伞]

真的。如果唯一的选择是null，Today或Tomorrow，那么一个可为null的日期时间似乎是多余的。