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.

[Flags]
public enum DatePartFlags
{


   Ticks=0,
   Year=1,
   Month=2,
   Day=4,
   Hour=8,
   Minute=16,
   Second=32,
   Millisecond=64
};

[Flags]
public enum DtMask
{
    // make conformant to MS guidelines again:
    // define a meaningful 0-value
    Ticks       = 0,
    Year        = (1<<0),
    Month       = (1<<1), 
    Day         = (1<<2),
    Hour        = (1<<3),
    Minute      = (1<<4),
    Second      = (1<<5),
    Millisecond = (1<<6),

    Full        = Ticks, 
    Date        = Day|Month|Year,
    Time        = Hour|Minute|Second|Millisecond,
};

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 ||).

        public static bool Equal(this DateTime now, DateTime then, DtMask mask)
        {
            // Caution: 0-value always match in HasFlag(), use therefore "=="
            return mask == DtMask.Full ? now == then
                :  (!mask.HasFlag(DtMask.Millisecond) || now.Millisecond == then.Millisecond)
                && (!mask.HasFlag(DtMask.Second)      ||      now.Second == then.Second)
                && (!mask.HasFlag(DtMask.Minute)      ||      now.Minute == then.Minute)
                && (!mask.HasFlag(DtMask.Hour)        ||        now.Hour == then.Hour)
                && (!mask.HasFlag(DtMask.Day)         ||         now.Day == then.Day)
                && (!mask.HasFlag(DtMask.Month)       ||       now.Month == then.Month)
                && (!mask.HasFlag(DtMask.Year)        ||        now.Year == then.Year);
        }

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