Enum parsing from strings in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to parse the string "Red" into the Color enum.

C Sharp (C#)

Color color = (Color) Enum.Parse(typeof(Color), [1]);

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

A"Red"

BRed

Ccolor

Dtypeof(Color)

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the enum name without quotes causes a compile error.

Passing the enum type instead of the string name.

The Enum.Parse method requires the string name of the enum value, so it must be passed as a string literal like "Red".

2fill in blank

medium

Complete the code to safely parse the string "Blue" into the Color enum using TryParse.

C Sharp (C#)

bool success = Enum.TryParse<Color>([1], out Color color);

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

Acolor

Btypeof(Color)

C"Blue"

DBlue

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the enum variable instead of the string.

Passing the enum type instead of the string.

The Enum.TryParse method requires the string to parse, so you must pass the string literal "Blue".

3fill in blank

hard

Fix the error in parsing the string "Green" to the Color enum using Enum.Parse.

C Sharp (C#)

Color color = (Color) Enum.Parse(typeof(Color), [1], true);

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

A"Green"

B"green"

CGreen

Dgreen

Attempts:

3 left

💡 Hint

Common Mistakes

Passing unquoted strings causes compile errors.

Passing the enum name without quotes.

The string must be passed with quotes and match the enum name case-insensitively because of the true ignoreCase parameter. So "Green" is correct.

4fill in blank

hard

Fill both blanks to parse "Yellow" ignoring case and assign to variable.

C Sharp (C#)

Color color = (Color) Enum.Parse(typeof(Color), [1], [2]);

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

A"Yellow"

Bfalse

Ctrue

DYellow

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the string.

Using false instead of true for ignoreCase.

The first blank needs the string "Yellow" and the second blank the boolean true to ignore case.

5fill in blank

hard

Fill all three blanks to parse string to enum, check success, and print result.

C Sharp (C#)

if (Enum.TryParse<Color>([1], out Color [2]))
{
    Console.WriteLine([3]);
}

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

A"Purple"

BparsedColor

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted strings.

Mismatching variable names between out parameter and print statement.

The string to parse is "Purple", the out variable is parsedColor, and we print parsedColor.

Practice

1. What does Enum.Parse do in C#?

easy

A. Checks if a string is a valid enum name without converting

B. Converts an enum value to a string

C. Creates a new enum type at runtime

D. Converts a string to the corresponding enum value

Solution

1. Step 1: Understand Enum.Parse purpose

   Enum.Parse takes a string and tries to convert it to the matching enum value.

2. Step 2: Compare options

   Only Converts a string to the corresponding enum value describes converting string to enum value. Others describe different actions.

3. Final Answer:

   Converts a string to the corresponding enum value -> Option D

4. Quick Check:

   Enum.Parse converts string to enum [OK]

Hint: Enum.Parse converts string to enum value directly [OK]

Common Mistakes:

• Thinking Enum.Parse converts enum to string
• Confusing Enum.Parse with Enum.TryParse
• Believing Enum.Parse checks validity without conversion

2. Which of the following is the correct syntax to parse a string "Monday" to an enum DayOfWeek using Enum.Parse?

easy

A. DayOfWeek day = Enum.Parse("Monday");

B. DayOfWeek day = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), "Monday");

C. DayOfWeek day = Enum.Parse(DayOfWeek, "Monday");

D. DayOfWeek day = Enum.TryParse("Monday", out DayOfWeek day);

Solution

1. Step 1: Recall Enum.Parse syntax

   The correct syntax requires specifying the enum type with typeof and casting the result.

2. Step 2: Analyze options

   DayOfWeek day = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), "Monday"); matches the correct syntax: cast the result of Enum.Parse(typeof(EnumType), string).

3. Final Answer:

   DayOfWeek day = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), "Monday"); -> Option B

4. Quick Check:

   Enum.Parse needs typeof and cast [OK]

Hint: Use typeof(Enum) and cast result for Enum.Parse [OK]

Common Mistakes:

• Omitting typeof(EnumType)
• Not casting the result to enum type
• Confusing Enum.Parse with Enum.TryParse syntax

3. What will be the output of this code?

enum Color { Red, Green, Blue }

string input = "Green";
Color c = (Color)Enum.Parse(typeof(Color), input);
Console.WriteLine(c);

medium

A. Green

B. Runtime error

C. Blue

D. Red

Solution

1. Step 1: Parse string to enum

   The string "Green" matches the enum member Color.Green, so Enum.Parse returns that value.

2. Step 2: Print enum value

   Console.WriteLine prints the enum member name, which is "Green".

3. Final Answer:

   Green -> Option A

4. Quick Check:

   Enum.Parse("Green") = Color.Green [OK]

Hint: Enum.Parse returns enum matching string name [OK]

Common Mistakes:

• Expecting numeric value instead of name
• Assuming case-insensitive parsing by default
• Thinking it throws error for valid names

4. What is wrong with this code snippet?

enum Status { Active, Inactive }

string input = "Pending";
Status s = (Status)Enum.Parse(typeof(Status), input);
Console.WriteLine(s);

medium

A. It will print "Pending"

B. It will parse to Status.Active by default

C. It will throw a runtime exception

D. It will return null

Solution

1. Step 1: Check if input matches enum members

   The string "Pending" is not a member of Status enum, so Enum.Parse cannot convert it.

2. Step 2: Understand Enum.Parse behavior on invalid input

   Enum.Parse throws a runtime exception if the string does not match any enum name.

3. Final Answer:

   It will throw a runtime exception -> Option C

4. Quick Check:

   Invalid string causes Enum.Parse exception [OK]

Hint: Enum.Parse throws error if string not in enum [OK]

Common Mistakes:

• Expecting default enum value on invalid string
• Thinking it returns null instead of error
• Confusing with Enum.TryParse behavior

5. You want to safely convert a string "Sunday" to enum DayOfWeek without risking exceptions. Which code snippet correctly does this?

hard

A. bool success = Enum.TryParse("Sunday", true, out DayOfWeek day);

B. DayOfWeek.TryParse("Sunday", out DayOfWeek day);

C. Enum.TryParse(typeof(DayOfWeek), "Sunday", out DayOfWeek day);

D. DayOfWeek day = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), "Sunday");

Solution

1. Step 1: Understand safe parsing with Enum.TryParse

   Enum.TryParse returns a bool indicating success and outputs the parsed enum value.

2. Step 2: Check correct method signature

   bool success = Enum.TryParse("Sunday", true, out DayOfWeek day); uses Enum.TryParse with ignoreCase=true and out parameter, matching correct safe parsing syntax.

3. Final Answer:

   bool success = Enum.TryParse("Sunday", true, out DayOfWeek day); -> Option A

4. Quick Check:

   Enum.TryParse with out and ignoreCase is safe [OK]

Hint: Use Enum.TryParse with out and ignoreCase for safe parse [OK]

Common Mistakes:

• Using Enum.Parse which throws exceptions
• Calling TryParse on enum type instead of Enum class
• Ignoring the out parameter requirement