Partial DateTime Object Equality

Introduction

I herein refer to the original post of http://www.codeproject.com/Tips/148065/Partial-DateTime-Object-Equality and offer some alterantive approch.

You may employ more of the native C# support for this partial DateTime Equality function:

1. Define the enum flags with bit shift operator instead of manually calculated powers of two values
2. Use Enum.HasFlag() on the mask instead of a self-invented function.
3. Use boolean logic to directly calculate the boolean result instead of over the re-calculation of some flag values.

Using the code

Alternative definition of the Equality Mask:

Use bit-shift instead of hardcoded values.

  1  [Flags]
  2  public enum DatePartFlags
  3  {
  4  
  5  
  6     Ticks=0,
  7     Year=1,
  8     Month=2,
  9     Day=4,
 10     Hour=8,
 11     Minute=16,
 12     Second=32,
 13     Millisecond=64
 14  };

  1  [Flags]
  2  public enum DtMask
  3  {
  4      // make conformant to MS guidelines again:
  5      // define a meaningful 0-value
  6      Ticks       = 0,
  7      Year        = (1<<0),
  8      Month       = (1<<1), 
  9      Day         = (1<<2),
 10      Hour        = (1<<3),
 11      Minute      = (1<<4),
 12      Second      = (1<<5),
 13      Millisecond = (1<<6),
 14  
 15      Full        = Ticks, 
 16      Date        = Day|Month|Year,
 17      Time        = Hour|Minute|Second|Millisecond,
 18  };

An alternative Equals method:

Use the HasFlag() method that is defined on all enum types.

In addition, you might use the direct logic that allows for shortcut evaluation for the first failure (usage of && and ||).

  1  public static bool Equal(this DateTime now, DateTime then, DtMask mask)
  2  {
  3      // Caution: 0-value always match in HasFlag(), use therefore "=="
  4      return mask == DtMask.Full ? now == then
  5          :  (!mask.HasFlag(DtMask.Millisecond) || now.Millisecond == then.Millisecond)
  6          && (!mask.HasFlag(DtMask.Second)      ||      now.Second == then.Second)
  7          && (!mask.HasFlag(DtMask.Minute)      ||      now.Minute == then.Minute)
  8          && (!mask.HasFlag(DtMask.Hour)        ||        now.Hour == then.Hour)
  9          && (!mask.HasFlag(DtMask.Day)         ||         now.Day == then.Day)
 10          && (!mask.HasFlag(DtMask.Month)       ||       now.Month == then.Month)
 11          && (!mask.HasFlag(DtMask.Year)        ||        now.Year == then.Year);
 12  }

History