Asynchronous programming is essential for building responsive applications, but it comes with challenges - particularly when you need to cancel operations.
Here's how to safely implement cancellation in C#.
The key to proper cancellation is the CancellationTokenSource class. This provides a token that can be passed to async methods and monitored for cancellation requests.
CancellationTokenSource
// Create a cancellation source with timeout var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10)); var token = cts.Token; try { // Pass token to async operations await DoLongRunningTaskAsync(token); } catch (OperationCanceledException) { // Handle cancellation gracefully Console.WriteLine("Operation was canceled"); } finally { // Always dispose the CancellationTokenSource cts.Dispose(); }
When writing cancellable async methods, check for cancellation at appropriate points:
async Task DoLongRunningTaskAsync(CancellationToken token) { // Check before starting expensive work token.ThrowIfCancellationRequested(); for (int i = 0; i < 100; i++) { // Periodically check during loops if (token.IsCancellationRequested) { // Clean up resources if needed CleanupResources(); // Then throw the standard exception throw new OperationCanceledException(token); } await Task.Delay(100, token); // Built-in methods accept tokens } }
token.ThrowIfCancellationRequested()
OperationCanceledException
By following these patterns, you can ensure your async operations respond promptly to cancellation requests while maintaining clean, resource-efficient code.
Reading a file line by line is useful when handling large files without loading everything into memory at once.
✅ Best Practice: Use File.ReadLines() which is more memory efficient.
Example
foreach (string line in File.ReadLines("file.txt")) { Console.WriteLine(line); }
Why use ReadLines()?
Reads one line at a time, reducing overall memory usage. Ideal for large files (e.g., logs, CSVs).
Alternative: Use StreamReader (More Control)
For scenarios where you need custom processing while reading the contents of the file:
using (StreamReader reader = new StreamReader("file.txt")) { string? line; while ((line = reader.ReadLine()) != null) { Console.WriteLine(line); } }
Why use StreamReader?
Lets you handle exceptions, encoding, and buffering. Supports custom processing (e.g., search for a keyword while reading).
When to Use ReadAllLines()? If you need all lines at once, use:
string[] lines = File.ReadAllLines("file.txt");
Caution: Loads the entire file into memory—avoid for large files!
String interpolation, introduced in C# 6.0, provides a more readable and concise way to format strings compared to traditional concatenation (+) or string.Format(). Instead of manually inserting variables or placeholders, you can use the $ symbol before a string to directly embed expressions inside brackets.
string name = "Walt"; string job = 'Software Engineer'; string message = $"Hello, my name is {name} and I am a {job}"; Console.WriteLine(message);
This would produce the final output of:
Hello, my name is Walt and I am a Software Engineer
String interpolation can also be chained together into a multiline string (@) for even cleaner more concise results:
string name = "Walt"; string html = $@" <div> <h1>Welcome, {name}!</h1> </div>";
In C#, you can format an integer with commas (thousands separator) using ToString with a format specifier.
int number = 1234567; string formattedNumber = number.ToString("N0"); // "1,234,567" Console.WriteLine(formattedNumber);
Explanation:
"N0": The "N" format specifier stands for Number, and "0" means no decimal places. The output depends on the culture settings, so in regions where , is the decimal separator, you might get 1.234.567.
Alternative:
You can also specify culture explicitly if you need a specific format:
using System.Globalization; int number = 1234567; string formattedNumber = number.ToString("N0", CultureInfo.InvariantCulture); Console.WriteLine(formattedNumber); // "1,234,567"
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