如何在UWP平台中使用ToOADate函数将DateTime值转换为OADate格式？

Question

我正在使用DateTime.FromOADate（）和DateTime.ToOADate（）函数在WPF和WinForms平台中将DateTime值转换为OADate格式。但是UWP平台没有哪些功能可用。因此，任何人都可以建议您的意见，以便在UWP平台中将dateTime值转换为OADate格式。

Answer 1

如何在UWP平台中使用ToOADate函数将DateTime值转换为OADate格式？

您可以通过引用.Net reference source来编写自己的ToOADate方法。例如，以下是您可以测试的ToOADate和FromOADate函数的简单演示。

private void btndatetime_Click(object sender, RoutedEventArgs e) 
{ 
    DateTime fromOA = FromOAdate(40967.6424503935); 
    System.Diagnostics.Debug.WriteLine(fromOA); 
    double toOA = ToOAdate(fromOA); 
    System.Diagnostics.Debug.WriteLine(toOA); 
} 
public DateTime FromOAdate(double oadate) 
{ 
    return new DateTime(DoubleDateToTicks(oadate), DateTimeKind.Unspecified); 
} 
public double ToOAdate(DateTime datetime) 
{ 
    return TicksToOADate(datetime.Ticks); 
} 
private const long TicksPerMillisecond = 10000; 
private const long TicksPerSecond = TicksPerMillisecond * 1000; 
private const long TicksPerMinute = TicksPerSecond * 60; 
private const long TicksPerHour = TicksPerMinute * 60; 
private const long TicksPerDay = TicksPerHour * 24; 
private const UInt64 TicksMask = 0x3FFFFFFFFFFFFFFF; 
private const long DoubleDateOffset = DaysTo1899 * TicksPerDay; 
// Number of days in a non-leap year 
private const int DaysPerYear = 365; 
// Number of days in 4 years 
private const int DaysPer4Years = DaysPerYear * 4 + 1;  // 1461 
// Number of days in 100 years 
private const int DaysPer100Years = DaysPer4Years * 25 - 1; // 36524 
// Number of days in 400 years 
private const int DaysPer400Years = DaysPer100Years * 4 + 1; // 146097 
private const int DaysTo1899 = DaysPer400Years * 4 + DaysPer100Years * 3 - 367; 
// Number of milliseconds per time unit 
private const int MillisPerSecond = 1000; 
private const int MillisPerMinute = MillisPerSecond * 60; 
private const int MillisPerHour = MillisPerMinute * 60; 
private const int MillisPerDay = MillisPerHour * 24; 
private static double TicksToOADate(long value) 
{ 
    if (value == 0) 
     return 0.0; // Returns OleAut's zero'ed date value. 
    if (value < TicksPerDay) // This is a fix for VB. They want the default day to be 1/1/0001 rathar then 12/30/1899. 
     value += DoubleDateOffset; // We could have moved this fix down but we would like to keep the bounds check.   
    long millis = (value - DoubleDateOffset)/TicksPerMillisecond; 
    if (millis < 0) 
    { 
     long frac = millis % MillisPerDay; 
     if (frac != 0) millis -= (MillisPerDay + frac) * 2; 
    } 
    return (double)millis/MillisPerDay; 
} 
internal static long DoubleDateToTicks(double value) 
{ 
    // The check done this way will take care of NaN 
    //if (!(value < OADateMaxAsDouble) || !(value > OADateMinAsDouble)) 
    // throw new ArgumentException(Environment.GetResourceString("Arg_OleAutDateInvalid")); 
    // Conversion to long will not cause an overflow here, as at this point the "value" is in between OADateMinAsDouble and OADateMaxAsDouble 
    long millis = (long)(value * MillisPerDay + (value >= 0 ? 0.5 : -0.5)); 
    // The interesting thing here is when you have a value like 12.5 it all positive 12 days and 12 hours from 01/01/1899 
    // However if you a value of -12.25 it is minus 12 days but still positive 6 hours, almost as though you meant -11.75 all negative 
    // This line below fixes up the millis in the negative case 
    if (millis < 0) 
    { 
     millis -= (millis % MillisPerDay) * 2; 
    } 

    millis += DoubleDateOffset/TicksPerMillisecond; 
    //if (millis < 0 || millis >= MaxMillis) throw new ArgumentException(Environment.GetResourceString("Arg_OleAutDateScale")); 
    return millis * TicksPerMillisecond; 
}