Review tasks

Practical tasks by course topic to check your knowledge. Each task is a separate program.

Topic 1. Git version control

1. Create a C# "Temperature converter" console program (Celsius, Fahrenheit, Kelvin) in a new Git repository with .gitignore and .gitattributes files created from dotnet new templates; record the development in at least four commits with meaningful messages, and show git status, git log --oneline, and the changes of the last commit with git show --stat.
2. Create a C# "Task tracker" console program (tasks with a priority and a deadline) in a Git repository, create the branches feature/priority and feature/deadline, make a commit in each, merge the first branch with a fast-forward and the second with a three-way merge after a new commit on main; delete the merged branches and show git log --oneline --graph --all.
3. Create a C# "Phone book" console program (names and phone numbers) in a Git repository, change the same output line in the feature/format branch and on main, merge the branch, resolve the merge conflict (in the terminal or in Visual Studio 2026), check the build, and complete the merge; show the conflict markers, git status during the conflict, and the history graph after the merge.
4. Create a C# "Cinema box office" console program (showings and ticket sales) in a Git repository and make two erroneous commits: undo the first with git revert, remove the second with git reset --hard HEAD~1, and then restore it with git reflog; show git log --oneline after each action and explain when it is acceptable to use git reset.
5. Create a C# "Attendance tracker" console program (students and attended classes) in a Git repository, start a change in the feature/report branch, stash the unfinished work with git stash push -m, switch to main, fix and commit a bug, return to the branch, restore the stash, and finish the change with a commit; show git stash list and git log --oneline --graph --all.
6. Create a C# "Body mass index calculator" console program (height, weight, BMI) in a Git repository and mark two of its versions with the annotated tags v1.0.0 and v1.1.0 with a description of the changes and a CHANGELOG.md file; show git tag -n, git diff --stat v1.0.0 v1.1.0, the contents of Program.cs in version 1.0.0 (git show v1.0.0:Program.cs), and temporarily switch to it with git switch --detach.
7. Create a C# "Warehouse inventory" console program (products and stock) in a Git repository, make three commits in the experiment/import branch, one of which fixes a bug that also exists on main; bring only this fix to main with git cherry-pick, rebase the branch onto main, and show that Git skipped the already applied commit.
8. Create a C# "Exam schedule" console program (course, date, room), an empty repository D:\Labs\remote\Exams.git, and two clones on behalf of two participants; both make commits, the second gets a git push rejection, runs git pull, resolves a conflict if necessary, and pushes the changes; show git log --oneline --graph in both clones and git remote -v.
9. Create a C# "Currency converter" console program (an amount and an exchange rate) in a Git repository with a history of at least six commits, one of which introduces a calculation bug; find this commit with git bisect, inspect it with git show and git blame, undo the bug with git revert, and show git log --oneline.
10. Create a C# "Budget tracker" console program (income and expenses) in a Git repository and a pre-commit hook in the .githooks folder that runs dotnet build and aborts the commit if the build fails; enable the folder with git config core.hooksPath .githooks, and show a rejected commit with a compilation error and a successful commit after the fix.

Topic 2. Regular expressions

11. Create a console program that asks the user for a postal code (five digits), a phone number +380XXXXXXXXX, and a date dd.mm.yyyy, checks each value with the Regex.IsMatch method with the ^ and \z anchors, additionally checks that the date exists with the DateOnly.TryParseExact method, and prints "valid" for each field or a description of the expected format.
12. Create a console program that asks the user for a text and a word, finds all occurrences of the word as a whole word case-insensitively (\b boundaries, Regex.Escape), and prints the number of matches and the position of each.
13. Create a console program that asks for lines LastName FirstName, CS-21, 87 until an empty line is entered, parses them with a pattern with named groups (last name, first name, group, a score from 0 to 100), rejects invalid lines with a message, and prints a table of students and the average score of each group.
14. Create a console program that reads text from a file, replaces yyyy-mm-dd dates with dd.mm.yyyy using group substitution, and dollar prices $12.50 with prices in hryvnias at a rate entered by the user using the Replace method with a MatchEvaluator, and prints the result and the number of replacements of each kind.
15. Create a console program that asks for a line of numbers separated by any number of commas, semicolons, spaces, or tabs, splits it with the Regex.Split method, checks each number with the TryParse method, and prints the sum, the average, and the invalid elements.
16. Create a console program that asks for a password, checks it with a single pattern with lookaheads (at least 10 characters, an uppercase and a lowercase letter, a digit, no spaces), and if the check fails, determines and prints all the violated rules with separate patterns.
17. Create a console program that reads a text file with Windows line endings, in RegexOptions.Multiline mode finds lines that start with the words HACK or FIXME case-insensitively, and prints the number of each line and the text after the keyword without the \r character.
18. Create a console program with a static partial class in which patterns for an email address, a Ukrainian IBAN, and a postal code are declared with the [GeneratedRegex] attribute; the program reads values from a file (one per line) and prints a table "value – type – format valid".
19. Create a console program that asks for a number of characters n, builds a string of n letters a and a ! character, checks it with the pattern ^(a+)+$ with a 200 ms timeout, catches RegexMatchTimeoutException, and then checks the same string with the RegexOptions.NonBacktracking option and the equivalent pattern ^a+$, printing the time of each check.
20. Create a console program that reads an application log file with lines 2026-09-17 10:15:32 [ERROR] text, counts the entries by level (INFO, WARN, ERROR), replaces the numbers in the error texts with N to group identical messages, and prints the five most frequent error messages with their counts.

Topic 3. Windows Forms fundamentals

21. Create a Windows Forms application in which the user enters the lengths of the three sides of a triangle in text fields and, after clicking the Calculate button, sees the perimeter, the area by Heron's formula, and the type of the triangle. Invalid values (not numbers, non-positive numbers, sides that do not form a triangle) are marked with an ErrorProvider component.
22. Create a Windows Forms "User registration" application with fields for a login (3–20 Latin letters and digits), an email, a password, and a password confirmation. The fields are validated in Validating events with an ErrorProvider, the Cancel button closes the form without validation, and the Register button shows a MessageBox only when the data is valid.
23. Create a Windows Forms application for ordering coffee with a choice of drink (RadioButton), size (ComboBox), extras (CheckBox), and quantity (NumericUpDown). The price is updated after every change by one shared event handler, and the Order button shows the order summary in a MessageBox.
24. Create a Windows Forms application with a list of cities in a ListBox and a city name input field with Add, Remove, and Sort buttons. Empty names and duplicates are not added (a message in a MessageBox), the Remove button is available only when a city is selected, and a label shows the number of cities.
25. Create a Windows Forms "Questionnaire" application with labels and fields laid out in a TableLayoutPanel and OK and Cancel buttons anchored to the bottom-right corner of the form (Anchor). When the window is resized, the fields stretch, the form has a minimum size, and the Enter and Esc keys press the corresponding buttons.
26. Create a Windows Forms "Notepad" application with a File main menu (New, Open…, Save As…, Exit) with shortcut keys, a multiline text field filling the whole form, and a status bar with the number of characters. Files are opened and saved through OpenFileDialog and SaveFileDialog, and read and write errors are shown in a MessageBox.
27. Create a Windows Forms "Countdown timer" application in which the user sets the minutes and seconds in NumericUpDown controls and starts, pauses, and resets the countdown with buttons. A Timer component updates the label every second, and when the countdown ends the form changes its background color and shows a MessageBox.
28. Create a Windows Forms application with a main form with a list of products and a modal form for adding a product (name, price, quantity) with OK and Cancel buttons. The modal form validates the fields and closes with DialogResult.OK only when the data is valid; the main form adds the product and shows the total cost.
29. Create a Windows Forms "Student records" application with a DataGridView table bound to a BindingList<T> through a BindingSource, and fields for the last name, group, and average score (60–100) with Add and Delete buttons. The status bar shows the number of students and the group's average score.
30. Create a Windows Forms application that, while the mouse moves over a panel, shows the cursor coordinates in the status bar, after a left click adds an "X, Y" point to a ListBox, after Ctrl+Z is pressed (the form's KeyDown event with KeyPreview) removes the last point, and whose list context menu contains the Copy (copy the points to the clipboard) and Clear commands.

Topic 4. GDI+ graphics

31. Create a Windows Forms application that in the OnPaint method draws a house made of a rectangle, a triangular roof (FillPolygon), hatched windows, and a sun circle; the drawing scales to the window size and does not disappear after the window is minimized.
32. Create a Windows Forms application that draws three rectangles filled with SolidBrush, HatchBrush, and LinearGradientBrush brushes, with the brush names as labels centered in the rectangles; the hatch style is chosen in a ComboBox.
33. Create a Windows Forms application in which text entered in a field is displayed in a frame in the center of the window; the font size is automatically chosen with MeasureString so that the text takes up no more than 80 % of the window width.
34. Create a Windows Forms application that plots the function y = $x^2$ − 4 on an interval given by the user (the start is less than the end) with axes, ticks, and labels; mathematical coordinates are converted to pixels with the Matrix class.
35. Create a Windows Forms application that creates a 400 × 300 Bitmap, draws a 5 × 5 multiplication table with borders in it, and saves the image to a PNG file chosen in a SaveFileDialog; the image is shown in a PictureBox.
36. Create a Windows Forms application that opens an image and converts it to a negative with the GetPixel and SetPixel methods, showing the original and the result; an invalid file is reported without crashing the program.
37. Create a Windows Forms application in which the user draws rectangles with the mouse (press, drag, release), all rectangles are stored in a list, and a right click deletes the rectangle under the cursor.
38. Create a Windows Forms application in which a ball (a circle) moves and bounces off the edges of the window on a Timer, the speed is changed with the "+" and "−" keys, and the animation does not flicker thanks to double buffering.
39. Create a custom BatteryIndicator control with a Level property (0–100) with the Category, Description, and DefaultValue attributes that draws a battery with charge segments, and a form on which the level is changed with a TrackBar.
40. Create a Windows Forms application that draws five shapes (a circle, a square, a triangle, a star, an ellipse) as GraphicsPath objects and, after a mouse click, prints the name of the shape under the cursor in the status bar (an IsVisible check).

Topic 5. Asynchrony with async/await

41. Create a Windows Forms application that, after a button is clicked, counts in Task.Run the number of primes up to the entered number (no more than 50,000,000). During the calculation the button is disabled, the cursor shows a wait state, and the result and the time are printed in a label.
42. Create a Windows Forms "Notes" application that asynchronously opens and saves text files (File.ReadAllTextAsync, File.WriteAllTextAsync) through the common dialogs and shows read and write errors in a MessageBox without blocking the interface.
43. Create a Windows Forms application that simulates a long-running operation of ten steps (Task.Delay of 500 ms each) with progress in a ProgressBar through IProgress<int> and a Cancel button; after cancellation a label shows the number of the step at which the operation was stopped.
44. Create a Windows Forms application that asynchronously copies a selected file into a selected folder in 1 MB chunks with progress in percent and a Cancel button; after cancellation the partially copied file is deleted.
45. Create a Windows Forms application that starts five simulated downloads of different durations at the same time, shows the completion time of each in a list (Task.WhenAll), and the name of the fastest one (Task.WhenAny).
46. Create a Windows Forms application that performs a simulated operation of a random duration from 1 to 5 s with a timeout set in a NumericUpDown; if the operation does not finish in time, it is canceled, and a label shows "Timeout".
47. Create a Windows Forms application that processes 20 simulated tasks (Task.Delay of a random duration), running no more than a given number at the same time (SemaphoreSlim), and shows in a label the current and the maximum number of tasks running at the same time.
48. Create a Windows Forms application that asynchronously processes several selected text files at the same time (a word count); if some files could not be read, the application shows the results of the successful files and a list of all errors (Task.WhenAll, Exception.InnerExceptions).
49. Create a Windows Forms application that asynchronously reads a large text file line by line through a method that returns IAsyncEnumerable<string> and adds the lines containing an entered word to a ListBox as soon as they are found, with the ability to cancel.
50. Create a Windows Forms application in which a background task generates a random temperature measurement every second and updates a label and a list of the last 10 measurements without cross-thread access errors (Control.InvokeAsync or IProgress<T>), and buttons start and stop the measurements.

Topic 6. DI, configuration, logging

51. Create a console program in which the IMessageSender interface has two implementations (email and SMS, console output), the OrderService service receives it through its constructor, and the implementation is chosen by the registration in the ServiceCollection according to the word email or sms entered by the user.
52. Create a console program that registers three services with the Singleton, Scoped, and Transient lifetimes, creates two scopes, and prints the IDs of the instances obtained in each scope, as well as messages about the objects being disposed.
53. Create a console program in which three payment methods (card, cash, transfer) are registered as keyed IPayment services; the user enters an amount and a method, and for an unknown method the program prints the list of available ones.
54. Create a console program with a host and a BackgroundService that every N seconds (N in appsettings.json) logs the current time and the iteration number, and after Ctrl+C logs the total number of iterations.
55. Create a console program with a host that prints the values of the App:Name and App:Port keys and the environment name and demonstrates overriding the values from appsettings.json with an appsettings.Development.json file, an environment variable, and a command-line argument.
56. Create a console program with a host in which the Smtp section (server, port 1–65535, sender address) is bound to an options class with ValidateDataAnnotations and ValidateOnStart validation, and the program prints the options or exits with an error message.
57. Create a console program with a host that reads a database connection string from user secrets, prints it with the password hidden, and reports if the secret is not set; describe the dotnet user-secrets commands for the setup.
58. Create a console program in which an order processing service receives an ILogger<T> and writes structured messages with the OrderId and Amount fields at different levels, and the minimum level for the service's category is set in appsettings.json.
59. Create a Windows Forms application with a host in which the main form is created by the container and receives a calculator service and an ILogger<T> through its constructor, and every calculation is logged.
60. Create a library with a service that determines whether a store is open (the opening hours in IOptions<T>, the time from TimeProvider) and xUnit.net unit tests with FakeTimeProvider and NullLogger<T> for the boundaries of the working hours.

Topic 7. SQL and ADO.NET

61. Create an SQL script for PostgreSQL that creates the departments and employees tables with identity primary keys, a foreign key, and NOT NULL, UNIQUE (email), and CHECK (a positive salary) constraints, fills them with five rows, and prints the employees with the department names.
62. Create an SQL script for the products table (name, category, price, quantity) that adds products with an INSERT … RETURNING statement, raises the prices of products of a given category by 5 %, deletes products with zero quantity, and prints the state of the table after each statement.
63. Create an SQL script that, for the students table (name, group, year of admission, average score), prints the students of a group with a score from 75 to 90 sorted by score in descending order, and also finds students whose last name starts with a given letter (ILIKE).
64. Create an SQL script for the authors, books, and book_authors (N:M) tables that prints the books with all their authors, the authors without books (LEFT JOIN), and the number of books of each author.
65. Create an SQL script for the orders table (customer, date, amount) that prints the number and total of orders by month and the customers with an order total over 10,000 UAH (GROUP BY, HAVING).
66. Create a C# console program that connects to PostgreSQL through an NpgsqlDataSource (the connection string in user secrets) and prints all rows of the cities table (name, population) as an aligned table, reading them with an NpgsqlDataReader with NULL checks.
67. Create a C# console program that asks for part of a product name and prints the matching products from the products table of a PostgreSQL database with a parameterized ILIKE query; show that the input ' OR '1'='1 does not return all rows.
68. Create a C# console program that prints the number of records and the minimum and maximum price in the products table with the ExecuteScalarAsync method, and adds a product entered from the keyboard with validation with the ExecuteNonQueryAsync method.
69. Create a C# console program that transfers an amount between two accounts of the accounts table in an NpgsqlTransaction: if there are insufficient funds or the account does not exist, the transaction is rolled back with a message.
70. Create a Windows Forms application that fills a DataTable from the employees table and shows it in a DataGridView with search by last name and the number of records in the status bar; connection errors are shown in a MessageBox.

Topic 8. Entity Framework Core

71. Create a C# console program with EF Core and PostgreSQL with "Author" and "Book" entities (a 1:N relationship), create the tables with a migration, add three books by two authors, and print the authors with the number of their books.
72. Create a C# console program with EF Core in which the "Product" model is configured through the Fluent API: a name of up to 100 characters with a unique index, a numeric(10,2) price, and a CHECK constraint on non-negative stock; the program adds a product and handles constraint violations with a message.
73. Create a C# console program with EF Core that, for the "Category" and "Product" entities, asks for a category name and prints its products loaded through Include, sorted by price; a missing category is reported.
74. Create a C# console program with EF Core in which students and courses are related N:M; the program asks for a student and a course, enrolls the student in the course (a repeated enrollment is rejected), and prints the student's courses.
75. Create a C# console program with EF Core that asks for a minimum and a maximum price (the minimum is not greater than the maximum) and prints the products in this range with a projection to a (Name, Category, Price) record sorted by name.
76. Create a C# console program with EF Core that prints, for each category, the number of products and the average and maximum price, calculated in the database through GroupBy, sorted by the number of products.
77. Create a C# console program with EF Core that asks for a page number and a page size (from 1 to 50) and prints the corresponding page of the list of customers sorted by last name, and the total number of pages.
78. Create a C# console program with EF Core with a menu for the "Note" entity: add, change the text, delete by number, and print all notes; changes are saved with SaveChangesAsync, and a nonexistent number is reported.
79. Create a C# console program with EF Core that asks for a category and a discount percentage (from 1 to 90) and changes the prices of all products of the category with a single ExecuteUpdateAsync call, printing the number of changed products.
80. Create a C# console program with EF Core that transfers an amount between two accounts in an explicit transaction (an insufficient balance cancels the transfer), and a conflict from a concurrent change of an account is detected with the xmin token and handled with a message.

Topic 9. Networking and sockets

81. Create a TCP server and a TCP client as console programs: the client sends lines entered by the user, and the server returns each line with its characters reversed together with its length; an empty line ends the session, and after the client disconnects the server waits for the next one.
82. Create a TCP server that serves several clients at the same time, keeps a counter of messages received from all clients, and replies to each message with its number, and a console client; the server prints client connections and disconnections to the console.
83. Create a TCP announcement server that broadcasts every message received from a client to all connected clients with the sender's name, and a console client with a separate task for receiving messages.
84. Create a TCP server with a protocol of the commands SUM numbers, MAX numbers, and QUIT that replies with the codes 200, 400 (invalid arguments), and 404 (unknown command), and a console client that prints the server's responses.
85. Create console programs that transfer an array of integers over TCP: the client sends the count of numbers and the numbers themselves in network byte order (BinaryPrimitives), and the server reads them with the ReadExactlyAsync method and returns the sum and the average.
86. Create a TCP server and client that exchange JSON messages (one object per line): the client sends a student's data (name, group, grades), and the server returns an object with the average score and the verdict "passed" if the average is at least 60.
87. Create a UDP sender that sends datagrams with lines entered by the user to 127.0.0.1:6200, and a UDP receiver that prints each datagram with the sender's address and the total number of datagrams received.
88. Create a UDP server that replies to a WHO broadcast request with its name and TCP port, and a client that sends the request to the broadcast address, collects replies for 3 s, and prints the list of servers found.
89. Create a TCP client that connects to a server with a 3 s timeout, waits no longer than 5 s for a response, and prints clear messages for a refused connection, a timeout, and a broken connection, and a server that replies to a request with a random delay of 0–8 s.
90. Create a Windows Forms application that connects to a TCP server at the address and port from text fields, sends a line from an input field, and shows the server's responses in a ListBox without blocking the interface, as well as a console echo server for testing.

Topic 10. REST web services

91. Create an ASP.NET Core Minimal API "Product catalog" web service with in-memory data and GET, POST, PUT, DELETE endpoints for the /api/products resource that return the codes 200, 201 with a Location header, 204, and 404.
92. Create a Minimal API "Class timetable" web service in which the route GET /api/lessons/{day:int:range(1,7)} returns the classes of a day of the week, and a request with a day number out of range gets 404.
93. Create a Minimal API "Library" web service whose GET /api/books endpoint supports the query string parameters author, year, page, and pageSize (1–20) and returns a page of books with the total number found.
94. Create a Minimal API "Course registration" web service in which the handlers have the return types Results<Created<T>, Conflict> and Results<Ok<T>, NotFound>, and a repeated registration of the same email for a course returns 409.
95. Create a Minimal API "Questionnaires" web service that, with AddValidation and the [Required], [Range], [EmailAddress] attributes, validates a questionnaire (name, age 16–100, email) and returns errors in the ProblemDetails format; unhandled exceptions are also returned as ProblemDetails with code 500.
96. Create a Minimal API "Cinema" web service with a route group /api/halls and a nested group /api/halls/{hallId}/seats, shared OpenAPI tags, and an endpoint filter that logs the method, the address, and the execution time of every request.
97. Create a Minimal API "Student records" web service that stores data in a database through EF Core (AddDbContext), implements CRUD operations asynchronously, and returns the list of a group's students sorted by last name.
98. Create a Minimal API "Notes" web service with an OpenAPI document (AddOpenApi, MapOpenApi) and endpoint descriptions, as well as an .http file with an address variable, requests to all endpoints, and invalid requests (400, 404).
99. Create a console program that gets exchange rates in JSON format from the web service GET /api/rates with HttpClient, asks the user for an amount and currency codes, prints the conversion result, and reports service unavailability or a timeout.
100. Create a console program with an IHttpClientFactory typed client for a task web service (GET/POST /api/tasks) that adds a task entered by the user, prints the list as a table, and shows validation errors from the ProblemDetails body.

Topic 11. Real time with SignalR

101. Create an ASP.NET Core SignalR server with a NotesHub hub whose method accepts an author name and a note text and broadcasts them to all clients, and a console client that asks for a name, sends the lines you type, and prints the received notes with the time they were received.
102. Create a SignalR server with a Roll hub method that generates a random number from 1 to 6: the caller (Clients.Caller) receives the result, and the other clients (Clients.Others) receive the message "name rolled the die: N"; the console client sends a roll on the roll command.
103. Create a SignalR server with room groups in which a client joins a room with the join name command and leaves it with the leave command, and only the members of their room receive messages; an attempt to write outside a room is rejected with a HubException.
104. Create a strongly typed hub Hub<IWeatherClient> with a WeatherUpdated(city, temperature) client method and a console client in which the user enters a city and a temperature (from −60 to 60), and all clients print the updates; invalid data is rejected by the server.
105. Create a SignalR server that in OnConnectedAsync and OnDisconnectedAsync keeps a list of connected users (the name is passed in the query string) in a singleton service and sends everyone the updated list, and a console client that prints the list after every change.
106. Create a SignalR server with a chat hub (the SendMessage method broadcasts a name and a text to everyone) and a HubConnection console client that receives the hub address and the name as command-line arguments, validates them, handles server unavailability at startup with a message to the error stream and exit code 1, sends the lines you type, and prints the received messages.
107. Create a SignalR server with a chat hub that broadcasts a message name and text to all clients, and a Windows Forms client with name and message fields, a send button, and a message list to which messages are added from the On handler in a way that is safe for the UI thread; while there is no connection, the send button is unavailable.
108. Create a SignalR server with a hub that has methods for joining a group and sending a message to a group, and a console client with automatic reconnection that prints with timestamps the Reconnecting, Reconnected (a new connection ID), and Closed events and, after a reconnect, rejoins the group given as a command-line argument.
109. Create a SignalR server with a BackgroundService that every 2 s sends the current server time to all clients through IHubContext<THub>, and a POST /api/message endpoint that sends an entered text to everyone; the console client prints both types of messages.
110. Create a SignalR server with a streaming hub method that returns an IAsyncEnumerable<int> of primes up to N with a 200 ms pause, and a console client that asks for N (from 2 to 10,000), prints the numbers as they arrive, and cancels the stream when Enter is pressed.

Topic 12. WPF fundamentals

111. Create a WPF application with a registration form (login, a PasswordBox password, a password confirmation, a date of birth) laid out with a Grid panel with Auto and * columns. The Register button (IsDefault) validates the fields and shows errors in a TextBlock, and the Cancel button (IsCancel) closes the window.
112. Create a WPF application whose main window is laid out with a DockPanel: a menu at the top, a status bar at the bottom, a list of cities on the left, and a card of the selected city (name, population, description) on the right with a GridSplitter.
113. Create a WPF application with a panel of twelve color buttons on a UniformGrid, where one handler of the bubbling Click event attached to the panel changes the color of a preview rectangle and shows the color name, and e.Handled stops the event.
114. Create a WPF application with a field for entering a phone number in which the tunneling PreviewTextInput event lets through only digits, spaces, and a leading +, and the PreviewKeyDown event forbids pasting text with Ctrl+V with a message in the status bar.
115. Create a WPF application with a ListBox list of tasks, an input field, and Add, Remove, and Clear buttons. Empty tasks and duplicates are not added, Remove is available only for a selected task, and a label shows the number of tasks.
116. Create a WPF RatingControl user control with a Value dependency property (0–10, with coercion) and a callback method that updates the display, and a window in which a Slider is bound to the element's Value with ElementName.
117. Create a WPF application in which clicking a Canvas adds a circle at the click point (the Canvas.Left and Canvas.Top attached properties are set in code), the right mouse button deletes the circle under the cursor, and a label shows the number of circles.
118. Create a WPF application with a list of products and a modal window for adding a product (name, price, quantity) with OK and Cancel buttons. The window closes with DialogResult = true only when the data is valid, and the main window adds the product and shows the total cost.
119. Create a WPF "Notepad" application with a File menu (Open, Save, Exit), a toolbar, and a text field, where the menu items and buttons use the built-in ApplicationCommands.Open and Save commands with Executed and CanExecute handlers, and the Ctrl+O and Ctrl+S keys work without extra code.
120. Create a WPF application that chooses a folder with an OpenFolderDialog, shows the list of the folder's text files in a ListBox, and after a file is selected shows its content in a TextBox and its size in the status bar; read errors are shown in a MessageBox.

Topic 13. Data binding and MVVM

121. Create a WPF application in which the first and last name fields are bound to a ViewModel with INotifyPropertyChanged, a label with the full name is updated while typing, and the label's font size is bound to a Slider through ElementName.
122. Create a WPF application following the MVVM pattern with a list of students (ObservableCollection<T>) shown in a ListBox through a DataTemplate, fields for adding a student, and an Add command that is unavailable when the name is empty.
123. Create a WPF application that shows a list of products with a price and, with a custom IValueConverter, displays the price as the words "cheap", "moderate", or "expensive" depending on bounds passed as the converter parameter.
124. Create a WPF application with a registration form (login, email, age) in which the ViewModel implements INotifyDataErrorInfo, errors are shown with a border and a tooltip, and the save button is unavailable while there are errors.
125. Create a WPF application with a button style in the window resources that changes the font under the mouse cursor through a Trigger, and a style based on the first one (BasedOn) for the delete button.
126. Create a WPF application with a round button whose look is set by a custom ControlTemplate with TemplateBinding and IsMouseOver and IsPressed triggers, and a light and dark theme switch through DynamicResource.
127. Create a WPF application following the MVVM pattern with a list of cities (name, region, population), search while typing, and sorting by population through ICollectionView.
128. Create a WPF application in which a counter is incremented and decremented by commands based on a custom RelayCommand : ICommand class, and the decrement command is unavailable when the value is zero.
129. Create a WPF "Shopping list" application on CommunityToolkit.Mvvm with the [ObservableProperty] and [RelayCommand] attributes, add and delete commands, and a label with the number of items.
130. Create a class library with a discount calculator ViewModel on CommunityToolkit.Mvvm, a WPF application that uses it, and xUnit.net unit tests that check the calculation and the command's unavailability for invalid data.

Topic 14. WPF animation and multimedia

131. Create a WPF application in which a logo made of shapes (Ellipse, Path) with a gradient brush rotates by 360° in 2 s after a click on it; the center of rotation is the center of the logo, and a repeated click during the rotation is ignored.
132. Create a WPF application in which buttons under the cursor smoothly grow by 10 % and return to their normal size when the cursor leaves them (a style with an IsMouseOver trigger, EnterActions, and ExitActions).
133. Create a WPF application in which a rectangle, after a button is clicked, moves across the canvas to the right in 1 s, changes its background color with a ColorAnimation, and returns back (AutoReverse) twice; a slider sets the duration of 0.5–5 s.
134. Create a WPF application with an animated loading bar described by a storyboard in the resources and Start, Pause, Resume, Stop buttons; after completion the status bar shows "Done", and after a pause the current storyboard time.
135. Create a WPF application in which a notification appears from above with a bounce (a ThicknessAnimation with BounceEase), stays for 3 s, and disappears with an opacity animation; a button shows the notification with an entered text, and an empty text is not accepted.
136. Create a WPF application in which a ball travels a path through four keyframes (linear, discrete, spline, and eased), and a list lets you choose the easing function of the last frame (BounceEase, ElasticEase, CubicEase).
137. Create a WPF application in which a ball thrown with a mouse click in the direction of the cursor moves under gravity and bounces off the walls and the floor with a loss of speed; the motion is calculated in CompositionTarget.Rendering from the frame time.
138. Create a WPF application with a field in which a click creates a circle that expands and disappears in 1 s (an animation from code with BeginAnimation); after the animation finishes, the circle is removed from the canvas.
139. Create a WPF video player application on MediaElement with Play/Pause and Stop buttons, a position slider that is updated by a timer and allows seeking, a time display, and a message if the file fails to open.
140. Create a WPF application with three sound buttons that play WAV files from the program folder with the MediaPlayer class, have a shared volume slider, and show in the status bar the sound duration or a message about a missing file.

Topic 15. Cross-platform .NET MAUI

141. Create a .NET MAUI application with one page on which a Grid lays out fields for entering weight and height, a Calculate button, and a label with the body mass index. The buttons have an explicit style with x:Key, and the text colors are set through AppThemeBinding for the light and dark themes.
142. Create a .NET MAUI application that shows a list of students (last name, group, average score) in a CollectionView with an item template, an EmptyView for an empty list, and an Add button that adds a student from input fields after validating the data.
143. Create a .NET MAUI application with a settings page on which a Switch toggles the dark theme (UserAppTheme), a Slider sets the font size of a sample text, and the chosen values are stored in Preferences and restored after a restart.
144. Create a .NET MAUI "Counter" application with a ViewModel on CommunityToolkit.Mvvm ([ObservableProperty], [RelayCommand]), +1, −1, and Reset buttons, and compiled x:DataType bindings; the −1 button is unavailable when the value is zero.
145. Create a .NET MAUI application with two Shell pages: a list of cities and a city details page. The details page route is registered in AppShell, the city name is passed as a string query parameter, and the details page receives it through IQueryAttributable.
146. Create a .NET MAUI "Notes" application in which the note text is stored in a file in FileSystem.AppDataDirectory, loaded when the page appears, and the Save and Delete buttons save and delete the file with a DisplayAlertAsync message.
147. Create a .NET MAUI application that, after a button is clicked, checks and requests the Permissions.LocationWhenInUse permission, gets the device coordinates through Geolocation, and shows them with the distance to London; a denied permission and disabled location services are explained to the user.
148. Create a .NET MAUI application in which the Pick photo button opens MediaPicker, the selected photo is shown in an Image and copied to the application data folder, and the Take photo button is available only when IsCaptureSupported is true.
149. Create a simple ASP.NET Core Minimal API web service GET /api/products (name, price) and a .NET MAUI application that gets the list of products in JSON format through HttpClient, shows it in a CollectionView inside a RefreshView, and reports an error if the service is unavailable.
150. Create a .NET MAUI application in which a task list page and its ViewModel are registered in MauiProgram together with an ITaskStore storage service, the ViewModel receives the service through its constructor, and tasks are added, marked as done, and stored in a JSON file.

Topic 16. AI in .NET

151. Create a console chat program that, through IChatClient with a "bookstore consultant" system instruction, answers the user's questions in English, and for empty input or an unavailable model prints an error message.
152. Create a console chat program that keeps the conversation history in a List<ChatMessage>, trims it to the last 10 messages (the system one remains), and after each response prints the number of input and output tokens.
153. Create a console program that prints the model's response as a stream (GetStreamingResponseAsync) and lets you interrupt generation by pressing Esc through a CancellationToken, after which it prints "Cancelled".
154. Create a console program that sends the same request with temperature 0 and 1 three times each (ChatOptions), limits the response to 100 tokens, and prints the responses and the FinishReason as a table.
155. Create a console program that extracts a record EventInfo (name, date, city, price or null) from an entered event announcement text through GetResponseAsync<T>, checks the date and price in code, and reports an invalid model response.
156. Create a console program in which, to answer about exchange rates, the model calls the C# function GetRate(string currency) with in-memory rates; the function checks the three-letter currency code and returns a message about an unknown currency.
157. Create a console program that builds a ChatClientBuilder pipeline with UseLogging (the Debug level) and a custom middleware client that measures and prints the time of each request to the model.
158. Create a console program that creates embeddings of ten sentences from a file and, for an entered sentence, prints the three nearest ones with the cosine similarity calculated by TensorPrimitives.CosineSimilarity.
159. Create a console program that answers questions from a text file of rules: it finds the three nearest items by embeddings, passes them to the model with the instruction to answer only from them, and prints the answer with the item numbers.
160. Create a class library with a TicketClassifier service that uses IChatClient to determine the category of a request, and xUnit unit tests with a fake IChatClient that check a valid response, invalid JSON, and model unavailability.