Underlying numeric values in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an enum named Color.

C Sharp (C#)

[1] Color { Red, Green, Blue }

Drag options to blanks, or click blank then click option'

Aclass

Benum

Cstruct

Dinterface

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'class' instead of 'enum' to declare an enumeration.

The keyword enum is used to declare an enumeration type in C#.

2fill in blank

medium

Complete the code to get the underlying numeric value of the enum member.

C Sharp (C#)

int value = (int)Color.[1];

Drag options to blanks, or click blank then click option'

ARed

BYellow

CPurple

DOrange

Attempts:

3 left

💡 Hint

Common Mistakes

Using a member name that does not exist in the enum.

To get the numeric value of an enum member, cast it to int and use the member name.

3fill in blank

hard

Fix the error in the code to correctly cast the enum to its underlying value.

C Sharp (C#)

var number = [1]Color.Green;

Drag options to blanks, or click blank then click option'

A(int)

B(double)

C(string)

D(bool)

Attempts:

3 left

💡 Hint

Common Mistakes

Casting enum to a non-numeric type like string or bool.

To get the numeric value of an enum member, cast it to int.

4fill in blank

hard

Fill both blanks to create a dictionary mapping enum members to their numeric values.

C Sharp (C#)

var dict = new Dictionary<Color, int> { [1], [2] };

Drag options to blanks, or click blank then click option'

A{Color.Red, (int)Color.Red}

B{Color.Yellow, (int)Color.Yellow}

C{Color.Green, (int)Color.Green}

D{Color.Blue, (int)Color.Blue}

Attempts:

3 left

💡 Hint

Common Mistakes

Using enum members that do not exist.

Not casting enum members to int for values.

The dictionary keys are enum members and values are their underlying int values.

5fill in blank

hard

Fill all three blanks to create a LINQ expression mapping enum members to their numeric values if the value is greater than 0.

C Sharp (C#)

var result = Enum.GetValues(typeof(Color)).Cast<Color>().Where([3] => (int)[3] > 0).ToDictionary([1] => [1], [1] => [2]);

Drag options to blanks, or click blank then click option'

Acolor

B(int)color

CColor

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Using the enum type name instead of a variable in the loop.

Not casting the enum member to int for the value.

This uses LINQ's ToDictionary method along with Where to map each qualifying enum member to its int value.

Practice

1. What is the underlying numeric value of an enum member in C# if not explicitly set?

easy

A. It starts at 0 and increments by 1 for each member

B. It is always 1 for all members

C. It is a random number assigned by the compiler

D. It must be manually assigned for each member

Solution

1. Step 1: Understand default enum numbering

   By default, C# assigns the first enum member the value 0.

2. Step 2: Check subsequent members

   Each following member increments by 1 automatically unless explicitly set.

3. Final Answer:

   It starts at 0 and increments by 1 for each member -> Option A

4. Quick Check:

   Default enum values start at 0 and increment [OK]

Hint: Remember enums start at zero unless you say otherwise [OK]

Common Mistakes:

• Thinking enums start at 1 by default
• Assuming enum values are random
• Believing manual assignment is always required

2. Which of the following is the correct way to get the numeric value of an enum member Day.Monday in C#?

easy

A. int value = Convert.ToInt32(Day.Monday.ToString());

B. int value = Day.Monday.ToInt();

C. int value = Day.Monday.Value;

D. int value = (int)Day.Monday;

Solution

1. Step 1: Recall casting enum to int

   In C#, you get the numeric value by casting the enum member to int using (int).

2. Step 2: Check other options

   Enums have no ToInt() method or Value property; Convert.ToInt32(Day.Monday.ToString()) parses the name ("Monday") and throws FormatException.

3. Final Answer:

   int value = (int)Day.Monday; -> Option D

4. Quick Check:

   Cast enum to int with (int) [OK]

Hint: Cast enum to int with (int) to get its number [OK]

Common Mistakes:

• Using non-existent methods like ToInt()
• Trying to access a Value property
• Converting enum.ToString() to int (parses name)

3. Given the enum:

enum Color { Red = 3, Green, Blue }

What is the output of this code?

Console.WriteLine((int)Color.Green);

medium

A. 4

B. 3

C. 1

D. 0

Solution

1. Step 1: Identify explicit enum value

   Color.Red is set to 3 explicitly.

2. Step 2: Understand implicit increment

   Color.Green is next, so it gets 4 (3 + 1).

3. Final Answer:

   4 -> Option A

4. Quick Check:

   Enum increments from explicit value [OK]

Hint: Next enum value increments by 1 from previous explicit value [OK]

Common Mistakes:

• Assuming Green is 1 by default
• Thinking Green equals Red's value
• Forgetting implicit increment after explicit value

4. What is wrong with this code snippet?

enum Status { Active = 1, Inactive = 1, Pending = 2 }

medium

A. Enum members cannot have duplicate values

B. Nothing is wrong; duplicate values are allowed

C. Enum members must be strings, not numbers

D. Enum members must be assigned sequentially starting at 0

Solution

1. Step 1: Check enum value rules

   C# allows enum members to share the same underlying numeric value.

2. Step 2: Verify other options

   Enum members can be numbers, do not need sequential values, and duplicates are allowed.

3. Final Answer:

   Nothing is wrong; duplicate values are allowed -> Option B

4. Quick Check:

   Duplicate enum values are valid in C# [OK]

Hint: Duplicate enum values are allowed in C# [OK]

Common Mistakes:

• Thinking duplicate enum values cause errors
• Believing enums must start at 0 and be sequential
• Confusing enum members with strings

5. You have this enum:

enum Level { Low = 1, Medium = 5, High = 10 }

Which code correctly checks if an integer variable score matches any enum value?

hard

A. bool isMatch = score >= (int)Level.Low && score <= (int)Level.High;

B. bool isMatch = (Level)score != null;

C. bool isMatch = Enum.IsDefined(typeof(Level), score);

D. bool isMatch = score == Level.Low || score == Level.Medium || score == Level.High;

Solution

1. Step 1: Understand Enum.IsDefined usage

   Enum.IsDefined checks if a given integer matches any enum member's underlying value.

2. Step 2: Analyze other options

   A checks range (includes invalid like 2); B casts int to enum (always succeeds) != null (always true); C direct int == enum comparisons do not compile without casting enum to int.

3. Final Answer:

   bool isMatch = Enum.IsDefined(typeof(Level), score); -> Option C

4. Quick Check:

   Use Enum.IsDefined to check valid enum values [OK]

Hint: Use Enum.IsDefined to check if int matches enum value [OK]

Common Mistakes:

• Casting int to enum without validation
• Checking range instead of exact enum values
• Comparing int directly to enum members without casting