What is the best way to determine if a System.DateTime is midnight?

Question

It seems that there are several possible ways to determine if a given System.DateTime represents midnight. What are the pros and cons of each? Is one more readable or perform better than the others?

EDIT: I believe that readability is more important than performance until profiling shows that there is an issue. That is why I asked about both.

Example 1

Public Function IsMidnight(ByVal value As Date) As Boolean
    Return value.TimeOfDay = TimeSpan.FromHours(0)
End Function

Example 2

Public Function IsMidnight(ByVal value As Date) As Boolean
    Return value.CompareTo(value.[Date]) = 0
End Function

Answer 1

Depends. Do you want to check for exactly midnight to the second, or just that it's the midnight hour?

For the midnight hour

Public Function IsMidnightHour(ByVal date as Date) As Boolean
  return date.Hour = 0
End Function

For midnight hour and minute

Public Function IsMidnightHourAndMinute(ByVal date as Date) As Boolean
  return date.Hour = 0 AndAlso date.Minute = 0
End Function

For purely simply, exactly midnight you can use your example. However that will include checks up to the millisecond which may not be what you want.

Answer 2

I'd check (using C# for the example):

bool isMidnight = value.TimeOfDay.Ticks == 0;

IMO, this is easier than using FromHours etc, and doesn't involve any extra multiplication (since Ticks defined the TimeSpan - all the other properties are calculated).

Answer 3

This is a bit of micro-optimizing, either method would work fine.

Anyhow, I think this is what would perform best:

Public Function IsMidnight(ByVal value As Date) As Boolean
   Return value.TimeOfDay.Ticks = 0
End Function

If you want understandable code, perhaps this is best:

Public Function IsMidnight(ByVal value As Date) As Boolean
   Return value.TimeOfDay = TimeSpan.Zero
End Function