File paths and Directory operations in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this directory creation code?

Consider the following C# code that creates a directory and checks if it exists. What will be printed?

C Sharp (C#)

using System;
using System.IO;

class Program {
    static void Main() {
        string path = "TestDir";
        Directory.CreateDirectory(path);
        Console.WriteLine(Directory.Exists(path));
    }
}

A True

B False

C Throws IOException

D Throws UnauthorizedAccessException

💡 Hint

Think about what Directory.CreateDirectory does if the directory already exists.

Directory.CreateDirectory creates the directory if it doesn't exist, or does nothing if it already exists. Directory.Exists returns true if the directory exists, so the output is True.

❓ Predict Output

intermediate

What does this code print about file paths?

Given this C# code snippet, what will be the output?

C Sharp (C#)

using System;
using System.IO;

class Program {
    static void Main() {
        string filePath = "C:\\Users\\Public\\Documents\\report.txt";
        Console.WriteLine(Path.GetFileName(filePath));
    }
}

A report.txt

B C:\Users\Public\Documents\report.txt

C report

D Documents

💡 Hint

Path.GetFileName returns the file name and extension from a full path.

Path.GetFileName extracts the file name with extension from the full path, so it returns 'report.txt'.

❓ Predict Output

advanced

What is the output of this code listing files?

This code lists files in a directory. What will it print?

C Sharp (C#)

using System;
using System.IO;

class Program {
    static void Main() {
        string dir = "TestDir";
        Directory.CreateDirectory(dir);
        File.WriteAllText(Path.Combine(dir, "file1.txt"), "Hello");
        File.WriteAllText(Path.Combine(dir, "file2.txt"), "World");
        var files = Directory.GetFiles(dir);
        Console.WriteLine(files.Length);
    }
}

A 1

B 2

C Throws DirectoryNotFoundException

D 0

💡 Hint

Files are created before listing, so count should reflect that.

Two files are created in the directory before calling GetFiles, so the length of the files array is 2.

❓ Predict Output

advanced

What error does this code raise when deleting a non-empty directory?

What happens when you run this code that tries to delete a directory containing files?

C Sharp (C#)

using System;
using System.IO;

class Program {
    static void Main() {
        string dir = "TestDir";
        Directory.CreateDirectory(dir);
        File.WriteAllText(Path.Combine(dir, "file.txt"), "data");
        Directory.Delete(dir);
        Console.WriteLine("Deleted");
    }
}

A Throws UnauthorizedAccessException

B Prints 'Deleted'

C Throws IOException

D Throws DirectoryNotFoundException

💡 Hint

Deleting a directory with files without recursive flag causes an error.

Directory.Delete without recursive flag throws IOException if the directory is not empty.

🧠 Conceptual

expert

How many items are in the resulting dictionary after this path manipulation?

Consider this C# code that uses DirectoryInfo and FileInfo objects. How many entries will the dictionary contain?

C Sharp (C#)

using System;
using System.Collections.Generic;
using System.IO;

class Program {
    static void Main() {
        string dir = "TestDir";
        Directory.CreateDirectory(dir);
        File.WriteAllText(Path.Combine(dir, "a.txt"), "A");
        File.WriteAllText(Path.Combine(dir, "b.txt"), "B");
        var dict = new Dictionary<string, long>();
        var directoryInfo = new DirectoryInfo(dir);
        foreach (var file in directoryInfo.GetFiles()) {
            dict[file.Name] = file.Length;
        }
        Console.WriteLine(dict.Count);
    }
}

A Throws IOException

B 0

C 1

D 2

💡 Hint

Each file in the directory is added as a dictionary entry.

Two files are created and added to the dictionary, so the count is 2.

Practice

1. Which C# class is used to check if a directory exists on your computer?

easy

A. Path

B. File

C. Directory

D. StreamReader

Solution

1. Step 1: Understand the purpose of Directory class

   The Directory class provides methods to work with folders, including checking if they exist.

2. Step 2: Identify the correct method for existence check

   Directory.Exists(path) returns true if the folder exists, which is what we need.

3. Final Answer:

   Directory -> Option C

4. Quick Check:

   Directory = Folder check [OK]

Hint: Use Directory class to manage folders easily [OK]

Common Mistakes:

• Confusing File class with Directory for folders
• Using Path class to check existence
• Trying to read folder like a file

2. Which of the following is the correct syntax to create a new directory named "Data" in C#?

easy

A. Directory.Create("Data");

B. File.CreateDirectory("Data");

C. Path.CreateDirectory("Data");

D. Directory.CreateDirectory("Data");

Solution

1. Step 1: Identify the correct method to create directories

   The Directory class has a method called CreateDirectory to make new folders.

2. Step 2: Check method names and classes

   Only Directory.CreateDirectory("Data") is valid syntax; others are incorrect or belong to wrong classes.

3. Final Answer:

   Directory.CreateDirectory("Data"); -> Option D

4. Quick Check:

   CreateDirectory method creates folders [OK]

Hint: Use Directory.CreateDirectory to make folders [OK]

Common Mistakes:

• Using Directory.Create instead of CreateDirectory
• Trying to create directory with File class
• Using Path class for folder creation

3. What will be the output of this C# code?

string folder = "C:\\Users\\Public";
string fileName = "report.txt";
string fullPath = Path.Combine(folder, fileName);
Console.WriteLine(fullPath);

medium

A. C:/Users/Public/report.txt

B. C:\Users\Public\report.txt

C. C:\Users\Publicreport.txt

D. C:\Users\Public\

Solution

1. Step 1: Understand Path.Combine behavior

   Path.Combine joins folder and file name with the correct directory separator for Windows (\).

2. Step 2: Check the combined string output

   The result is "C:\Users\Public\report.txt" with backslashes and a single separator between folder and file.

3. Final Answer:

   C:\Users\Public\report.txt -> Option B

4. Quick Check:

   Path.Combine joins paths with \ [OK]

Hint: Path.Combine joins paths with correct separators [OK]

Common Mistakes:

• Expecting forward slashes instead of backslashes
• Missing separator between folder and file
• Confusing output with folder path only

4. Identify the error in this code snippet that tries to delete a directory:

string path = "C:\\Temp";
if (Directory.Exists(path))
{
    Directory.Delete(path);
    Console.WriteLine("Deleted");
}

medium

A. Directory.Delete requires a second argument to delete non-empty folders

B. Directory.Exists should be File.Exists

C. The path string is incorrectly escaped

D. Console.WriteLine cannot be used inside if

Solution

1. Step 1: Understand Directory.Delete behavior

   Directory.Delete(path) without a second argument only deletes empty folders.

2. Step 2: Check if folder might be non-empty

   If folder has files, Directory.Delete(path, true) is needed to delete recursively.

3. Final Answer:

   Directory.Delete requires a second argument to delete non-empty folders -> Option A

4. Quick Check:

   Delete non-empty folder needs recursive flag [OK]

Hint: Use Directory.Delete(path, true) for non-empty folders [OK]

Common Mistakes:

• Assuming Directory.Delete deletes non-empty folders by default
• Using File.Exists to check folders
• Incorrectly escaping path strings

5. You want to list all subdirectories inside "C:\\Projects" and print their full paths. Which code snippet correctly does this?

hard

A. foreach (var dir in Directory.GetDirectories("C:\\Projects")) { Console.WriteLine(dir); }

B. foreach (var file in Directory.GetFiles("C:\\Projects")) { Console.WriteLine(file); }

C. foreach (var dir in Path.GetDirectories("C:\\Projects")) { Console.WriteLine(dir); }

D. foreach (var dir in Directory.ListDirectories("C:\\Projects")) { Console.WriteLine(dir); }

Solution

1. Step 1: Identify method to get subdirectories

   Directory.GetDirectories(path) returns an array of folder paths inside the given directory.

2. Step 2: Use foreach to print each directory path

   Looping over the array and printing each path is done with foreach and Console.WriteLine.

3. Final Answer:

   foreach (var dir in Directory.GetDirectories("C:\\Projects")) { Console.WriteLine(dir); } -> Option A

4. Quick Check:

   GetDirectories lists folders [OK]

Hint: Use Directory.GetDirectories to list folders [OK]

Common Mistakes:

• Using GetFiles instead of GetDirectories
• Trying to use Path class for directory listing
• Using non-existent Directory.ListDirectories method