Enum parsing from strings in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Enum parsing code?

Consider the following C# code that parses a string into an enum value. What will be printed?

C Sharp (C#)

using System;

enum Color { Red, Green, Blue }

class Program {
    static void Main() {
        string input = "Green";
        if (Enum.TryParse<Color>(input, out var color)) {
            Console.WriteLine((int)color);
        } else {
            Console.WriteLine("Parse failed");
        }
    }
}

A 1

B 0

C Parse failed

D 2

💡 Hint

Remember that enum values start at 0 by default and increment by 1.

The enum Color has Red=0, Green=1, Blue=2. Parsing "Green" succeeds and returns the enum value with underlying int 1.

❓ Predict Output

intermediate

What happens if parsing fails without TryParse?

What will happen when running this code?

C Sharp (C#)

using System;

enum Status { Active, Inactive }

class Program {
    static void Main() {
        string input = "Pending";
        var status = (Status)Enum.Parse(typeof(Status), input);
        Console.WriteLine(status);
    }
}

A Throws ArgumentException

B Prints 0

C Prints Pending

D Prints Active

💡 Hint

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

Since "Pending" is not a member of the Status enum, Enum.Parse throws an ArgumentException.

🔧 Debug

advanced

Why does this Enum.TryParse fail unexpectedly?

Look at this code snippet. It tries to parse a string to an enum but always fails. Why?

C Sharp (C#)

using System;

enum Direction { North, South, East, West }

class Program {
    static void Main() {
        string input = "north";
        if (Enum.TryParse<Direction>(input, out var dir)) {
            Console.WriteLine(dir);
        } else {
            Console.WriteLine("Failed to parse");
        }
    }
}

A The out variable dir is not declared correctly

B The enum Direction does not contain "north" because it is misspelled

C Enum.TryParse is case-sensitive by default, so "north" does not match "North"

D Enum.TryParse requires a third boolean parameter to work

💡 Hint

TryParse can be case-insensitive if you specify an option.

By default, Enum.TryParse is case-insensitive. The string "north" does not match the enum member "North" because of case difference.

📝 Syntax

advanced

Which option correctly parses a string ignoring case?

Choose the code snippet that correctly parses the string "west" to the enum Direction ignoring case.

C Sharp (C#)

enum Direction { North, South, East, West }

A Enum.TryParse<Direction>("west", out var d);

B Enum.Parse(typeof(Direction), "west", false);

C Enum.Parse<Direction>("west", true);

D Enum.TryParse<Direction>("west", out var d, true);

💡 Hint

Look for the overload of TryParse that accepts a boolean for case-insensitivity.

Option D uses Enum.TryParse with the third parameter ignoreCase=true, which allows parsing "west" ignoring case.

🚀 Application

expert

How many items are in the dictionary after parsing multiple enum strings?

Given this code, how many key-value pairs does the dictionary contain after execution?

C Sharp (C#)

using System;
using System.Collections.Generic;

enum Level { Low = 1, Medium = 2, High = 3 }

class Program {
    static void Main() {
        string[] inputs = { "Low", "Medium", "High", "low", "HIGH" };
        var dict = new Dictionary<Level, int>();
        foreach (var s in inputs) {
            if (Enum.TryParse<Level>(s, true, out var level)) {
                if (!dict.ContainsKey(level)) {
                    dict[level] = 0;
                }
                dict[level]++;
            }
        }
        Console.WriteLine(dict.Count);
    }
}

A 5

B 3

C 2

D 4

💡 Hint

Consider that parsing is case-insensitive and dictionary keys are unique enum values.

All strings parse to one of three enum values: Low, Medium, High. Case differences do not create new keys. So dictionary has 3 keys.