C#DateTime:当我只使用"时间"时使用什么"日期"？

Question

我DateTime在C#中使用a 来显示时间.在构建时间时,每个人都使用什么日期部分？

例如,以下内容无效,因为没有零日或零日:

// 4:37:58 PM
DateTime time = new DateTime(0, 0, 0, 16, 47, 58);

我使用COM的零日期吗？

// 4:37:58 PM
DateTime time = new DateTime(1899, 12, 30, 16, 47, 58);

或者也许是SQL Server的？

//4:37:58 PM
DateTime time = new DateTime(1900, 1, 1, 16, 47, 58);

我意识到这是随意的,因为我会忽略代码中的日期部分,但是能够使用它仍然是很好的:

DateTime duration = time2 - time1;

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回答

我想我喜欢MinValue

 DateTime time = DateTime.MinValue.Date.Add(new TimeSpan(16, 47, 58));

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注意:我不能使用a TimeSpan,因为它不会存储当天的时间.我知道的原因是因为没有办法将其内容显示为时间.

也就是说,TimeSpan记录一段时间,而不是一天中的时间,例如:

TimeSpan t = new TimeSpan(16, 47, 58);
t.ToString();

以小时:分钟:秒的格式返回一段时间,例如:

16:47:58

而不是时间:

4:47:58 PM    (United States)
04:47:58 nm   (South Africa)
4:47:58.MD    (Albania)
16:47:58      (Algeria)
04:47:58 ?    (Bahrain)
PM 4:47:58    (Singapore)
?? 04:47:58  (Taiwan)
04:47:58 PM   (Belize)
4:47:58 p.m.  (New Zealand)
4:47:58 ??    (Greece)
16.47.58      (Italy)
?? 4:47:58   (Korea)
04:47:58 ?.?  (Iran)
??? 04:47:58   (India)
04:47:58 p.m. (Argentina)
etc

换句话说,时间跨度和时间之间存在差异.并且还意识到,这TimeSpan并没有提供将时间跨度转换为一天中的时间的机制 - 这是有原因的.

Answer 1

那么DateTime.MinValue呢？

Answer 2

让我们帮助那些想要时间结构的人:

/// <summary>
/// Time structure
/// </summary>
public struct Time : IComparable
{
    private int minuteOfDay;
    public static Time Midnight = "0:00";
    private static int MIN_OF_DAY = 60 * 24;

    public Time(int minuteOfDay)
    {
        if (minuteOfDay >= (60 * 24) || minuteOfDay < 0)
            throw new ArgumentException("Must be in the range 0-1439", "minuteOfDay");
        this.minuteOfDay = minuteOfDay;
    }

    public Time(int hour, int minutes)
    {
        if (hour < 0 || hour > 23)
            throw new ArgumentException("Must be in the range 0-23", "hour");
        if (minutes < 0 || minutes > 59)
            throw new ArgumentException("Must be in the range 0-59", "minutes");

        minuteOfDay = (hour * 60) + minutes;
    }

    #region Operators
    public static implicit operator Time(string s)
    {
        var parts = s.Split(':');
        if (parts.Length != 2)
            throw new ArgumentException("Time must be specified on the form tt:mm");
        return new Time(int.Parse(parts[0]), int.Parse(parts[1]));
    }


    public static bool operator >(Time t1, Time t2)
    {
        return t1.MinuteOfDay > t2.MinuteOfDay;
    }
    public static bool operator <(Time t1, Time t2)
    {
        return t1.MinuteOfDay < t2.MinuteOfDay;
    }
    public static bool operator >=(Time t1, Time t2)
    {
        return t1.MinuteOfDay >= t2.MinuteOfDay;
    }
    public static bool operator <=(Time t1, Time t2)
    {
        return t1.MinuteOfDay <= t2.MinuteOfDay;
    }
    public static bool operator ==(Time t1, Time t2)
    {
        return t1.GetHashCode() == t2.GetHashCode();
    }
    public static bool operator !=(Time t1, Time t2)
    {
        return t1.GetHashCode() != t2.GetHashCode();
    }

    /// Time
    /// Minutes that remain to
    /// Time conferred minutes
    public static Time operator +(Time t, int min)
    {
        if (t.minuteOfDay + min < (24 * 60))
        {
            t.minuteOfDay += min;
            return t;
        }
        else
        {
            t.minuteOfDay = (t.minuteOfDay + min) % MIN_OF_DAY;
            return t;
        }
    }

    public static Time operator -(Time t, int min)
    {
        if (t.minuteOfDay - min > -1)
        {
            t.minuteOfDay -= min;
            return t;
        }
        else
        {
            t.minuteOfDay = MIN_OF_DAY + (t.minuteOfDay - min);
            return t;
        }
    }

    public static TimeSpan operator -(Time t1, Time t2)
    {
        return TimeSpan.FromMinutes(Time.Span(t2, t1));
    }
    #endregion


    public int Hour
    {
        get
        {
            return (int)(minuteOfDay / 60);
        }
    }
    public int Minutes
    {
        get
        {
            return minuteOfDay % 60;
        }
    }


    public int MinuteOfDay
    {
        get { return minuteOfDay; }
    }

    public Time AddHours(int hours)
    {
        return this + (hours * 60);
    }

    public int CompareTo(Time other)
    {
        return this.minuteOfDay.CompareTo(other.minuteOfDay);
    }

    #region Overrides
    public override int GetHashCode()
    {
        return minuteOfDay.GetHashCode();
    }

    public override string ToString()
    {
        return string.Format("{0}:{1:00}", Hour, Minutes);
    }
    #endregion

    /// 
    /// Safe enumerering - whatever interval applied max days 
    /// 
    /// Start time
    /// Spring in minutes
    /// 
    public static IEnumerable Range(Time start, int step)
    {
        return Range(start, start, step);
    }

    /// 
    /// Safe enumeration - whatever interval applied max days
    /// 
    public static IEnumerable Range(Time start, Time stop, int step)
    {
        int offset = start.MinuteOfDay;
        for (var i = 0; i < Time.Span(start, stop); i += step)
        {
            yield return Time.Midnight + (i + offset);
        }
    }

    /// 
    /// Calculates the number of minutes between t1 and t2
    /// 
    public static int Span(Time t1, Time t2)
    {
        if (t1 < t2) // same day
            return t2.MinuteOfDay - t1.MinuteOfDay;
        else // over midnight
            return MIN_OF_DAY - t1.MinuteOfDay + t2.MinuteOfDay;
    }
}

Answer 3

TimeSpan当然可以存储一天中的时间 - 您只需要将该值视为自午夜以来经过的时间量,基本上与我们读取时钟的方式相同.

Answer 4

我个人创建一个Time struct包含DateTime实例的自定义,它具有类似的属性,构造函数等,但不会暴露天/月/等.只需将所有公共访问者传递给包含的实例即可.然后你可以简单地将epoch作为一个private static readonly DateTime字段,并且你选择什么值并不重要,因为它整齐地包含在你的自定义结构中.在其余的代码中可以简单地写:

var time = new Time(16, 47, 58);