Underlying numeric values in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this enum underlying value code?

Consider the following C# code that defines an enum and prints its underlying numeric value. What will be printed?

C Sharp (C#)

enum Color { Red = 1, Green = 2, Blue = 4 }

class Program {
    static void Main() {
        Color c = Color.Blue;
        Console.WriteLine((int)c);
    }
}

A 3

B 0

C 2

D 4

💡 Hint

Look at the value assigned to Blue in the enum.

The enum Color assigns Blue the value 4 explicitly. Casting it to int prints 4.

❓ Predict Output

intermediate

What is the output when casting enum with default underlying values?

Given this enum and code, what number is printed?

C Sharp (C#)

enum Status { Pending, Approved, Rejected }

class Program {
    static void Main() {
        Status s = Status.Approved;
        Console.WriteLine((int)s);
    }
}

A 2

B 0

C 1

D 3

💡 Hint

Enums start numbering from 0 by default unless specified.

Pending is 0, Approved is 1, Rejected is 2. So Approved prints 1.

❓ Predict Output

advanced

What is the output of this enum with mixed explicit and implicit values?

Analyze this code and determine the output printed.

C Sharp (C#)

enum Level { Low = 3, Medium, High = 10, Critical }

class Program {
    static void Main() {
        Console.WriteLine((int)Level.Medium);
        Console.WriteLine((int)Level.Critical);
    }
}

A 4 and 11

B 3 and 10

C 4 and 10

D 3 and 11

💡 Hint

Implicit values increment from the previous value.

Medium is one more than Low (3), so 4. Critical is one more than High (10), so 11.

🧠 Conceptual

advanced

Which underlying type is used by default for enums in C#?

In C#, if you do not specify an underlying type for an enum, which numeric type does it use by default?

A short

B int

C byte

D long

💡 Hint

Think about the most common integer type in C#.

By default, enums use int as their underlying type unless specified otherwise.

❓ Predict Output

expert

What is the output of this code using Flags attribute and bitwise operations?

Consider this enum with the [Flags] attribute and the code below. What will be printed?

C Sharp (C#)

[Flags]
enum Permissions {
    None = 0,
    Read = 1,
    Write = 2,
    Execute = 4
}

class Program {
    static void Main() {
        Permissions p = Permissions.Read | Permissions.Write;
        Console.WriteLine((int)p);
    }
}

A 3

B 1

C 2

D 4

💡 Hint

Bitwise OR combines the numeric values.

Read is 1, Write is 2. OR operation 1 | 2 = 3.

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