Flags attribute and bitwise enums in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Flags attribute and bitwise enums

Define enum with Flags attribute

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Assign combined flags using bitwise OR

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Check flags using bitwise AND

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Use flags in conditions or output

This flow shows how to define an enum with Flags, combine values using bitwise OR, and check flags using bitwise AND.

Execution Sample

C Sharp (C#)

using System;
[Flags]
enum Days { None=0, Mon=1, Tue=2, Wed=4 }
class Program {
    static void Main() {
        Days meeting = Days.Mon | Days.Wed;
        bool hasTue = (meeting & Days.Tue) == Days.Tue;
        Console.WriteLine(meeting);
        Console.WriteLine(hasTue);
    }
}

This code defines a Flags enum for days, combines Monday and Wednesday, checks if Tuesday is included, and prints results.

Execution Table

Step	Action	Expression	Result	Explanation
1	Define enum Days with Flags	Days { None=0, Mon=1, Tue=2, Wed=4 }	Enum defined	Enum values assigned powers of two for bitwise use
2	Combine flags Mon and Wed	Days.Mon | Days.Wed	5	1 (Mon) OR 4 (Wed) = 5, combined flags value
3	Assign combined flags to meeting	meeting = 5	meeting = 5	meeting holds Mon and Wed flags
4	Check if Tue flag is set	(meeting & Days.Tue) == Days.Tue	(5 & 2) == 2	False, because 5 & 2 = 0, Tue not included
5	Print meeting	Console.WriteLine(meeting)	Mon, Wed	Flags enum prints combined names
6	Print hasTue	Console.WriteLine(hasTue)	False	Boolean result of Tue check
7	End	-	-	Program ends

💡 All steps executed; program ends after printing results.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
meeting	undefined	undefined	5 (Mon | Wed)	5 (unchanged)	5 (unchanged)
hasTue	undefined	undefined	undefined	False	False

Key Moments - 3 Insights

Why do we use powers of two (1, 2, 4, ...) for enum values?

Using powers of two ensures each flag corresponds to a unique bit, so they can be combined and checked independently as shown in step 2 and 4 of the execution_table.

Why does (meeting & Days.Tue) == Days.Tue return false when Tue is not set?

Because bitwise AND returns zero if the bit for Tue is not set in meeting. Step 4 shows (5 & 2) equals 0, so the condition is false.

How does printing the combined flags show 'Mon, Wed' instead of a number?

The Flags attribute tells C# to print combined flag names separated by commas, as seen in step 5 of the execution_table.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is the combined value of Days.Mon | Days.Wed?

A 5

B 3

C 6

D 7

💡 Hint

Check the 'Result' column in step 2 of the execution_table.

At which step does the program check if Tuesday is included in meeting?

A Step 3

B Step 5

C Step 4

D Step 6

💡 Hint

Look for the bitwise AND check in the execution_table.

If we add Days.Tue to meeting using bitwise OR, what would be the new value of meeting?

A 6

B 7

C 3

D 4

💡 Hint

Add the values 5 (Mon|Wed) and 2 (Tue) using bitwise OR: see step 2 for reference.

Concept Snapshot

[Flags] enum uses powers of two values
Combine flags with bitwise OR (|)
Check flags with bitwise AND (&)
Printing combined flags shows names
Use to represent multiple options in one variable

Full Transcript

This example shows how to use the Flags attribute with enums in C#. We define days with values 1, 2, 4 so each is a unique bit. We combine Monday and Wednesday using bitwise OR to get 5. We check if Tuesday is included by bitwise AND with 2, which returns false. Printing the combined flags shows 'Mon, Wed'. This technique lets us store multiple options in one variable and check them easily.