C# — 100 Coding Exercises

Name: C# — 100 Coding Exercises
Rating: 4.5 (132 reviews)

Level up your C# skills with 100 bite-sized, in-browser coding problems. Learn by doing—no setup needed.

Created byElegant Code – Krystyna Ślusarczyk

Last updated 5/2026

English

What you'll learn

Solve 100 practical C# coding problems in your browser
Build confidence through real hands-on practice
Master core topics like loops, collections, and LINQ
Tackle modern C# features
Prepare for C# interviews with real-world challenges
Instantly check solutions and learn from video walkthroughs

Coding Exercises

This course includes our updated coding exercises so you can practice your skills as you learn.

Course content

3 sections • 106 lectures • 4h 47m total length

Welcome! Basic information & how to get help1:40
50 seconds about your instructor0:50
What to expect from this course2:03
Coding exercises introduction & troubleshooting6:03
About videos with solutions0:43
Watch the instructor walk through the code step by step to show how each exercise is solved, and use the short, focused videos to compare your solution with mine.

Check if a collection contains any negative numbers (⭐)
Solution: Check if a collection contains any negative numbers1:50
Split a full name into first and last names (⭐)
Solution: Split a full name into first and last names1:24
Count character frequencies in a string (⭐⭐)
Solution: Count character frequencies in a string2:22
Count character frequencies in a word by iterating with a foreach loop to build a result dictionary, then validate with tests; alternatively solve it with linq using GroupBy and ToDictionary.
Filter and select qualified players from a game leaderboard (⭐⭐)
Solution: Filter and select qualified players from a game leaderboard3:25
Calculate total break time from multiple time ranges (⭐)
Solution: Calculate total break time from multiple time ranges1:51
Track the highest score for a player (⭐)
Solution: Track the highest score for a player1:58
Leverage the null conditional and null coalescing assignment operators to safely handle missing player data, initialize the highest score when needed, and update it when a higher score arrives.
Calculate shipping cost based on order total and customer status (⭐)
Solution: Calculate shipping cost based on order total and customer status1:57
Explore using a C# switch expression with when clauses to calculate shipping costs by order total and customer status, offering a concise alternative to if-else and validating with tests.
Try parsing a date and extracting its components (⭐)
Solution: Try parsing a date and extracting its components2:31
Check if a string is a palindrome (⭐)
Solution: Check if a string is a palindrome2:48
Implement a weekly schedule with multiple custom indexers (⭐⭐)
Solution: Implement a weekly schedule with multiple custom indexers4:43
Read file content safely (⭐)
Solution: Read file content safely2:05
Sum a range of values from a variable-length input (⭐)
Solution: Sum a range of values from a variable-length input2:19
sum the numbers in an array from a start index inclusive to an end index exclusive, handling negative starts or start greater than end, using the range operator and sum.
Separate strings and integers from a mixed object list (⭐)
Solution: Separate strings and integers from a mixed object list3:08
Sum integers with strict overflow checking (⭐)
Solution: Sum integers with strict overflow checking2:58
Safely sum integers into a long (⭐)
Solution: Safely sum integers into a long2:29
Format text with custom styles (⭐)
Solution: Format text with custom styles1:51
Override the base text formatter in derived classes, such as ShoutFormatter and WhisperFormatter, using virtual methods and string interpolation to trim, uppercase or lowercase, and wrap messages in distinct formats.
Read a string until the end marker (⭐)
Solution: Read a string until the end marker1:57
Extend DayOfWeek to detect weekends (⭐)
Solution: Extend DayOfWeek to detect weekends1:28
Learn to implement a C# extension method on DayOfWeek that detects weekends by checking Saturday and Sunday, using a static class and a static method with this parameter.
Count halvings until value drops below 1 (⭐)
Solution: Count halvings until value drops below 12:08
Send notifications via multiple channels (⭐⭐)
Solution: Send notifications via multiple channels2:57
Generate random discount codes (⭐⭐)
Solution: Generate random discount codes2:29
Validate user registration data (⭐⭐)
Solution: Validate user registration data4:46
Check if parentheses are balanced (⭐⭐⭐)
Solution: Check if parentheses are balanced3:07
Use a stack to check if parentheses are balanced: push opening, pop on closing; if you pop from empty or finish with a nonempty stack, return false; otherwise return true.
Add matrices with operator overloading (⭐⭐)
Solution: Add matrices with operator overloading2:55
Track class usage statistics (⭐)
Solution: Track class usage statistics1:36
Implement a log method in C# that prints messages with a unique id starting at 1, using a static constructor and string interpolation, and increment the id after each log.
Time duration adapter (⭐⭐)
Solution: Time duration adapter3:33
Count unique elements in a list (⭐)
Solution: Count unique elements in a list1:55
Generic pair type (⭐⭐)
Solution: Generic pair type2:33
Define a generic pair class in C# that holds two values of the same type; include read-only first and second properties, a constructor, and a swap method using tmp.
Unique task identifier with string formatting (⭐⭐)
Solution: Unique task identifier with string formatting3:18
Calculate factorial with recursion (⭐⭐)
Solution: Calculate factorial with recursion2:31
Check the result of the tic-tac-toe game (⭐⭐)
Solution: Check the result of the tic-tac-toe game5:57
Determine the tic-tac-toe winner by validating a 3x3 grid and checking rows, columns, and diagonals for X or O, using helper methods and a nullable result.
Event ticket composed ID (⭐)
Solution: Event ticket composed ID2:54
Produce Fibonacci sequence (⭐⭐⭐)
Solution: Produce Fibonacci sequence3:51
Calculate discounted price (⭐⭐)
Solution: Calculate discounted price3:45
Reverse a string without built-in methods (⭐)
Solution: Reverse a string without built-in methods2:20
Custom book sorting with IComparer (⭐⭐)
Solution: Custom book sorting with IComparer2:58
Learn to implement IComparer for custom sorting by book title, including a BookTitleComparer with a Compare method that handles nulls and uses case-insensitive string.Compare for List.Sort.
Sort houses by floor area with IComparable (⭐)
Solution: Sort houses by floor area with IComparable2:03
Recent messages by timestamp (⭐)
Solution: Recent messages by timestamp1:58
Sort messages by timestamp in descending order using LINQ, then map them to formatted strings. Format timestamps with ToString(format) or inline interpolated strings, and verify results with tests.
Define a value-based House data structure (⭐)
Solution: Define a value-based House data structure1:17
Handle web request errors with exception filtering (⭐⭐)
Solution: Handle web request errors with exception filtering3:15
Get top N recent messages by timestamp (⭐)
Solution: Get top N recent messages by timestamp1:30
Use LINQ to filter a timestamped message collection sorted oldest to newest, skipping messages before today with SkipWhile and taking the first N from the remainder.
Define a temperature converter with expression-bodied members (⭐)
Define a temperature converter with expression-bodied members2:01
Practice defining expression-bodied members in a temperature converter, including a constructor, a read only property, a Celsius property with getter and setter for a Kelvin field, and Fahrenheit conversion method.
Calculate land value with double and decimal (⭐⭐)
Solution: Calculate land value with double and decimal2:56
Implement a binary search algorithm for numbers (⭐⭐⭐)
Solution: Implement a binary search algorithm for numbers4:17
Implement shape calculations with abstract classes (⭐)
Solution: Implement shape calculations with abstract classes2:03
Find the cheapest product by category (⭐)
Solution: Find the cheapest product by category1:44
Implement a copy constructor for a book (⭐)
Solution: Implement a copy constructor for a book1:26
Implement a copy constructor for the book class that copies the fields and properties from another Book object, throws ArgumentNullException if null, and creates a new instance.
Process messages with IDisposable logger (⭐⭐)
Solution: Process messages with IDisposable logger3:00
Implement a sorting algorithm (⭐⭐)
Solution: Implement a sorting algorithm4:55
Practice implementing a simple sorting algorithm with bubble sort, swapping adjacent numbers across passes until the largest elements settle at the end, using a swap flag to stop early.
Flatten a nested list of numbers (⭐)
Solution: Flatten a nested list of numbers2:38
Chain constructors in a family of classes (⭐)
Solution: Chain constructors in a family of classes2:35
Describe a class without hardcoding names (⭐)
Solution: Describe a class without hardcoding names2:46
Merge two sequences with fallback defaults (⭐⭐)
Solution: Merge two sequences with fallback defaults3:43
Generate property report with reflection (⭐⭐)
Solution: Generate property report with reflection2:07
Transform numbers with a delegate (⭐⭐)
Solution: Transform numbers with a delegate3:14
Define a custom attribute (⭐⭐)
Solution: Define a custom attribute2:39
Process tasks one by one using a queue (⭐)
Solution: Process tasks one by one using a queue2:07
Limit list capacity with an indexer (⭐)
Solution: Limit list capacity with an indexer1:58
Reverse a generic array (⭐⭐)
Solution: Reverse a generic array2:15
Check if a type implements a specific interface (⭐⭐)
Solution: Check if a type implements a specific interface1:43
Explore how to determine if a type implements an interface using reflection, validating the interface with IsInterface and checking GetInterfaces with LINQ Any.
Raise an event when threshold is exceeded (⭐⭐⭐)
Solution: Raise an event when threshold is exceeded4:28
Serialize and deserialize an object using System.Text.Json (⭐)
Solution: Serialize and deserialize an object using System.Text.Json2:14
Implement a converter in c# to serialize a person object to json using the built‑in JsonSerializer and deserialize json back into a person object.
Yield unique words until encountering a duplicate (⭐⭐)
Solution: Yield unique words until encountering a duplicate1:49
Measure method execution time with Stopwatch (⭐)
Solution: Measure method execution time with Stopwatch1:34
Extract a slice of characters using Span (⭐⭐)
Solution: Extract a slice of characters using Span2:58
Learn how to extract a slice of a string using the Span type, given a starting index and length, and compare it with substring for memory-safe, efficient slicing in C#.
Return results as ValueTuple instead of anonymous objects (⭐⭐)
Solution: Return results as ValueTuple instead of anonymous objects2:45
Work with custom attributes and reflection to find marked methods (⭐⭐⭐)
Solution: Work with custom attributes and reflection to find marked methods3:48
Define a custom RunMe attribute for methods and implement GetMarkedMethodNames(type) to return names of methods decorated with RunMe using reflection, GetMethods with BindingFlags and bitwise or, then GetCustomAttribute to filter.
Merge two user collections with unique emails (⭐)
Solution: Merge two user collections with unique emails1:37
Merge two user collections into one by using LINQ UnionBy with email as the key, discarding duplicates from the second collection.
Extract values in brackets using StringBuilder (⭐⭐)
Solution: Extract values in brackets using StringBuilder3:02
Deprecate a base logging method using method hiding (⭐⭐)
Solution: Deprecate a base logging method using method hiding2:20
Calculate the average using INumber<T> constraint (⭐⭐)
Solution: Calculate the average using INumber<T> constraint4:08
Implement a generic CalculateAverage method using INumber<T> to work across numeric types via generic math. Sum all elements, then divide by the count to compute the average.
Create a simple dictionary of words using SortedList (⭐⭐)
Solution: Create a simple dictionary of words using SortedList4:06
Analyze a file path from segments (⭐)
Solution: Analyze a file path from segments4:16
Aggregate sales data by category (⭐⭐)
Solution: Aggregate sales data by category2:49
Filter out null strings from a list using nullable reference types (⭐⭐)
Solution: Filter out null strings from a list using nullable reference types3:24
Paginate a list of items (⭐)
Solution: Paginate a list of items2:27
Implement deferred object creation using Lazy<T> (⭐⭐)
Solution: Implement deferred object creation using Lazy<T>3:59
Implement deferred object creation with Lazy<T> to create the report only when the first access occurs, reuse it on later accesses, and avoid unnecessary work in ReportManager.
Format a column-aligned table using string interpolation (⭐⭐)
Solution: Format a column-aligned table using string interpolation3:33
Get basic system information (⭐⭐)
Solution: Get basic system information2:03
Query environment details with RuntimeInformation and Environment to return the operating system, number of logical processors, and whether the process is 64‑bit.
Divide integers into equal-sized chunks (⭐)
Solution: Divide integers into equal-sized chunks1:42
Split a collection of integers into full, equal-sized chunks with the GetFullChunks method, using LINQ's Chunk, throwing an exception for sizes below one and filtering to exclude incomplete final chunks.
Find the intersection of two collections (⭐⭐)
Solution: Find the intersection of two collections3:07
Implement a custom IEqualityComparer for product equality (⭐⭐)
Solution: Implement a custom IEqualityComparer for product equality3:00
Square a list of numbers in parallel (⭐⭐)
Solution: Square a list of numbers in parallel2:38
Convert a string array to a CSV line (⭐)
Solution: Convert a string array to a CSV line1:45
Calculate weighted average with nullable values (⭐⭐)
Solution: Calculate weighted average with nullable values2:35
Capitalize each word in a sentence (⭐⭐)
Solution: Capitalize each word in a sentence3:27
Create a generic extension method to double all values in a collection (⭐⭐)
Solution: Create a generic extension method to double all values in a collection2:17
Create a generic extension method for IEnumerable<T> that doubles all items by yielding each item twice, with proper null checks and static class requirements.
Format the main diagonal words in a 2D array (⭐⭐)
Solution: Format the main diagonal words in a 2D array2:50
Transform and log a list of numbers using Func and Action (⭐⭐)
Solution: Transform and log a list of numbers using Func and Action2:43
Flatten and filter a jagged string array (⭐⭐)
Solution: Flatten and filter a jagged string array3:13
Process jobs in order using a priority queue (⭐⭐)
Solution: Process jobs in order using a priority queue3:11
Calculate statistics from employee incomes (⭐⭐⭐)
Solution: Calculate statistics from employee incomes4:52
Practice computing basic statistics from a dataset of employee incomes by sorting to find min and max, using a LINQ average, and implementing median and mode with clear tie handling.
Perform an inner join on orders and customers (⭐⭐)
Solution: Perform an inner join on orders and customers2:59
Validate contest participants (⭐⭐)
Solution: Validate contest participants2:22
Validate a collection of contest participants, ensuring all are non-null, at least 18, with non-empty names and emails, and unique emails using LINQ All and a hashset.
Simulate a temperature sensor with threshold alerts (⭐⭐)
Solution: Simulate a temperature sensor with threshold alerts2:30
Create a value object for money with currency (⭐)
Solution: Create a value object for money with currency2:57
Override virtual and abstract methods in a baking product hierarchy (⭐)
Solution: Override virtual and abstract methods in a baking product hierarchy2:19
Group anagrams together from a list of words (⭐⭐)
Solution: Group anagrams together from a list of words2:46
Convert Roman numerals to integers (⭐⭐)
Solution: Convert Roman numerals to integers3:39
Generate a random wizard name (⭐)
Solution: Generate a random wizard name1:35
Generate a random wizard name by selecting a name and a title from two lists, then join them with the word the, using the next method on the random instance.

Requirements

Basic knowledge of C#

Description

Welcome to “C# — 100 Coding Exercises”—the most practical way to level up your C# skills, one problem at a time.

Learning to code isn’t just about watching videos—it’s about rolling up your sleeves and solving real problems. This course gives you 100 bite-sized, in-browser coding challenges, covering everything from the basics to advanced C# features. No setup or extra tools required—just open your browser and start coding.

Why practice with real coding exercises?

Mastering C# means practice, not just theory. These exercises are designed to help you really think in C#—so you’ll build the habits and confidence you need for any coding task.
Whether you’re preparing for job interviews, looking to sharpen your skills for your current job, or just love the satisfaction of solving problems, this course will get you there.
Each exercise is focused and practical, teaching core C# concepts, real-world problem-solving, and the kind of thinking that employers value.

What will you gain?

The ability to tackle a huge variety of real-world coding problems—loops, collections, LINQ, pattern matching, error handling, algorithms, and more.
Experience with modern C#—from tuple returns and nullable types, to reflection, operator overloading, custom attributes, and generic math.
The “muscle memory” to write code that’s clean, robust, and ready for interviews or professional work.
Step-by-step solutions for every exercise—you’ll get both a written explanation and a solution video (unlike many other exercise courses), so you can choose how you learn best.
For many problems, you’ll see more than one way to solve the task—helping you understand C# from multiple angles.

What makes this course different?

Hands-on learning—Solve every challenge directly in your browser. No downloads or installations needed.
Real variety—From simple tasks like string manipulation and list filtering to advanced problems involving generics, events, LINQ, and more. There’s something here for every level.
Immediate feedback—Submit your solution and see the results instantly, so you learn fast and keep improving.
Solution videos for every exercise—See the video walkthrough whenever you need them, or just check the written solution if you prefer.
Interview readiness—Practicing with real coding challenges is the best way to prepare for C# interviews and coding assessments.

Your path to C# mastery

I’m a .NET Technical Lead with 10+ years of industry experience, and I’ve built these exercises to help you build real, job-ready C# skills.
Whether you’re new to C#, coming back after a break, or just want to sharpen your edge, I’ll help you level up—one exercise at a time.

Additional perks:

Lifetime access and free updates—get all new exercises and improvements.
This course is covered by Udemy’s 30-day Refund Policy, so you can try it out risk-free.

Enroll now and start solving your way to C# mastery!

Who this course is for:

Ideal for anyone looking to sharpen their C# skills, prepare for interviews, or start a new job.

C# — 100 Coding Exercises

What you'll learn

Explore related topics

Coding Exercises

Course content

Introduction5 lectures • 11min

100 C# Coding Exercises100 lectures • 4hr 35min

Bonus section1 lecture • 2min

Requirements

Description

Who this course is for: