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Flags Attribute In Enums C#

In this article I will explain about Flags attribute in enums.

Software Requirement

Before you start reading this tutorial you should make sure that visual studio (any version) is installed on your machine.

Technical Knowledge

In order to understand this article you should know about

Basics of C#
What are enums?
How to create, compile and execute project using visual studio?
What is the purpose of Flags attribute?
Adding Flags attribute on enums means that enumerations will be treated as bit field.

Syntax

[Flags]
public enum Enum_Name {}

Example

Let us consider a scenario in which you are making an application for an election commission. In the application you have to set the eligibility criteria of the candidate who is participated in the election. A candidate must be

Above 18 years of age.
A resident of that country
A graduate
Without criminal background.

You write the following method

public bool IsEligibleToContestElection(bool above18, bool resident, bool graduate, bool nocriminalbackground) {
  if (above18 == true && resident == true && graduate == true && nocriminalbackground == true) return true;
  else return false;
}

And this is how you call this method

IsEligibleToContestElection(true, true, true, true)

The code looks fine. But in case the election commission asks you to add 10 more criteria for the eligibility of the candidate. Then you have to add 10 more input parameter in the function. So you will end up with function with multiple parameters which means that your code is not clean and is difficult to manage.

A very simple solution of the problem is to use enum with Flags attribute. So the above code could be rewritten as

[Flags]
public enum EligibilityCriteria {
  Above18,
  IsResident,
  AGraduate,
  NoCriminalBackground
}

public bool IsEligibleToContestElection(EligibilityCriteria criteria) {
  if (criteria == (EligibilityCriteria.Above18 & EligibilityCriteria.IsResident & EligibilityCriteria.AGraduate & EligibilityCriteria.NoCriminalBackground)) return true;
  else return false;
}

And this is how you can call this method

IsEligibleToContestElection(EligibilityCriteria.Above18 & EligibilityCriteria.IsResident & EligibilityCriteria.AGraduate & EligibilityCriteria.NoCriminalBackground)

So the code is cleaner and easy to manage.

Posted By -	Karan Gupta

Posted On -	Wednesday, October 29, 2014

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