Enumeration is one of the important features of C#. Enumeration allows you to name a variable to make sense for the program. It is in general impossible to understand numeric status values when there are more than two values for a single state of object. In such a case, we give a logical name for the numeric integer and use the logical name of it to call that particular state.
For instance:
Say you want to define the nature of a person.
public enum Character
{
Caring,
Honest,
Loving,
Desperate,
Obedient,
Logical,
Practical
}
You might name these characteristics using numeric values, say you have Honest
as 1, Loving
as 2, etc. But it would be more logical to use an Enum
instead.
Hmm... Putting it further, Enum
might also come in very handy when you want to use a combination of the same. Say for instance, a person can be both Logical
and Caring
. Now how could you define this? Do you need to define enumeration values for each of them? I guess that would not be a good choice either.
Flags
attribute in Enum
plays a vital role if you want to use the values of an enumeration in combinations. So that each combination of enumeration values are mutually exclusive and do not overlap with another value of Enum
. For bit fields, it is very easy and yet very handy to use Flags
attribute rather than using your own logic to define the flags yourself.
Steps to create BitField Enumeration
- Define each enumeration and set the value of each enumeration to be a power of 2.
- Put a
Flags
attribute for the enumeration.
Yes, it is so simple.
[Flags]
public enum Character : int
{
Caring =0,
Honest=1,
Loving=2,
Desperate=4,
Obedient=8,
Logical=16,
Practical=32
}
Hence the only thing that you need to do to declare a BitField
in .NET is to declare the values of enumeration as a multiple of 2 and apply a Flags
attribute to the type.
Hence the Character enumeration can now act in Bitwise Operators. The values of the Enumeration will look like:
00000000 0
00000001 1
00000010 2
00000100 4
00001000 16
00010000 32
00100000 64
01000000 128
Add Flag Combinations
To add more than one flag, you could use |
operator or bitwise OR
operator. Say for instance, you want to define a character which is both Caring
, Logical
and Practical
. In such a case, you could easily declare:
Character mycharacter = Character.Caring | Character.Logical | Character.Practical;
Here the mycharacter
variable will combine each of the values of Caring
, Logical
and Practical
using bitwise OR
operator.
Checking Flag Contains
&
Operator in Bitfield can be used to check whether the BitField contains the Flag
. Say for instance:
Character mycharacter = Character.Caring | Character.Logical | Character.Practical;
if ((mycharacter & Character.Caring) == Character.Caring)
Console.WriteLine("The man is caring");
Here the bitwise operator &
allows you to compare if mycharacter
has a certain flag
in it.
For Further Reading
To read more about Flags
attribute usage, you can go to the MSDN link and read the Usage Guidelines.
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