May 1, 2024
NEWS

C#: From Fundamentals to Advanced Techniques — A Comprehensive Cheat Sheet

Claudio Ctin016 mins
C#: From Fundamentals to Advanced Techniques — A Comprehensive Cheat Sheet

The comprehensive C# Cheat Sheet is designed to aid developers in mastering key syntax and concepts related to C# programming.

Contents

Basic Structure

Data Types

Variables

Constants

Conditional Statements

Loops

Arrays

Lists

Dictionaries

Methods

Classes & Objects

Exception Handling

Delegates, Events & Lambdas

LINQ (Language-Integrated Query)

Attributes

Async/Await

Miscellaneous

String Manipulation

File I/O

Date & Time

Generics

Nullables

Attributes & Reflection

Extension Methods

Dependency Injection

Partial Classes

Interoperability

Anonymous Types

Tuples

Pattern Matching

Local Functions

Records

with Expressions

Indexers and Ranges

using Declaration

Nullable Reference Types (NRTs)

Pattern-Based Using

Property Patterns

Default Interface Implementations

Dynamic Binding

1. Basic Structure

All C# programs follow a fundamental structure, outlined below:

using System;

public class HelloWorld
{
public static void Main(string[] args)
{
Console.WriteLine(“Hello, World!”);
}
}

Starting with .NET 5, top-level statements simplify the Program.cs content:

Console.WriteLine(“Hello, World”);

2. Data Types

C# supports various data types such as:

Value Types: int, char, float

Reference Types: string, class, array

3. Variables

Variables are symbolic names for values:

int age = 30; // integer variable
string name = “John”; // string variable
double PI = 3.14159; // double for floating-point numbers
bool isLoggedIn = true; // boolean variable

Use ‘var’ for type inference:

var number = 5; // compiler infers type as int
var message = “This is a message”; // compiler infers type as string

4. Constants

Constants hold immutable values:

const double GRAVITY = 9.81; // constant for gravitational acceleration
const string COMPANY_NAME = “MyCompany”; // constant company name

5. Conditional Statements

Control program flow based on conditions:

int age = 20;

if (age >= 18)
{
Console.WriteLine(“You are eligible to vote.”);
}
else
{
Console.WriteLine(“You are not eligible to vote.”);
}

switch (variable) { /*…*/ } // Switch statement

6. Loops

Execute code repeatedly:

for (int i = 1; i <= 5; i++)
{
Console.WriteLine(i);
}

foreach (var item in collection) { /*…*/ } // Foreach loop

while (condition) { /*…*/ } // While loop

do { /*…*/ } while (condition); // Do-while loop

7. Arrays

Fixed-size collections of elements:

string[] names = new string[3] { “Alice”, “Bob”, “Charlie” };
Console.WriteLine(names[1]); // Output: Bob (accessing element at index 1)

8. Lists

Dynamic collections similar to arrays:

List<int> numbers = new List<int>();
numbers.Add(1);
numbers.Add(2);
numbers.Add(3);

foreach (var number in numbers)
{
Console.WriteLine(number);
}

9. Dictionaries

Key-value pairs for data association:

Dictionary<string, string> phonebook = new Dictionary<string, string>();
phonebook.Add(“John Doe”, “123-456-7890”);
phonebook.Add(“Jane Doe”, “987-654-3210”);

Console.WriteLine(phonebook[“John Doe”]); // Output: 123-456-7890

10. Methods

Encapsulate reusable logic:

public class Rectangle
{
public double Width { get; set; }
public double Height { get; set; }

public double GetArea()
{
return Width * Height;
}
}

public class Program
{
public static void Main(string[] args)
{
Rectangle rect = new Rectangle();
rect.Width = 5;
rect.Height = 10;

double area = rect.GetArea();
Console.WriteLine($”Area of rectangle: {area}”);
}
}

11. Classes & Objects

Classes define blueprints for objects:

public class MyClass // Class definition
{
public string PropertyName { get; set; } // Properties store data
public void MethodName() { /*…*/ } // Methods define actions
}

MyClass obj = new MyClass(); // Object creation

12. Exception Handling

Manage runtime errors gracefully:

public static int GetNumberInput()
{
while (true)
{
try
{
Console.WriteLine(“Enter a number: “);
string input = Console.ReadLine();
return int.Parse(input);
}
catch (FormatException)
{
Console.WriteLine(“Invalid input. Please enter a number.”);
}
}
}

public static void Main(string[] args)
{
int number = GetNumberInput();
Console.WriteLine($”You entered: {number}”);
}

13. Delegates, Events & Lambda

For event-driven programming and method handling:

public delegate void MyDelegate(); // Delegate declaration

event MyDelegate MyEvent; // Event declaration

public class Person
{
public string Name { get; set; }
public int Age { get; set; }
}

public static void Main(string[] args)
{
List<Person> people = new List<Person>()
{
new Person { Name = “Alice”, Age = 30 },
new Person { Name = “Bob”, Age = 25 },
new Person { Name = “Charlie”, Age = 40 },
};

people.Sort((p1, p2) => p1.Name.CompareTo(p2.Name));

foreach (var person in people)
{
Console.WriteLine(person.Name); // Output: Alice, Bob, Charlie (sorted by name)
}
}

14. LINQ (Language-Integrated Query)

Query capabilities for data manipulation:

using System.Linq;

public static void Main(string[] args)
{
List<int> numbers = new List<int>() { 1, 2, 3, 4, 5, 6 };
var evenNumbers = numbers.Where(x => x % 2 == 0);

foreach (var number in evenNumbers)
{
Console.WriteLine(number); // Output: 2, 4, 6
}
}

15. Attributes

Add metadata to code elements:

[Obsolete(“Use the new DoSomethingV2 method instead.”)]
public void DoSomething()
{
// Implementation here
}

public void DoSomethingV2()
{
// New and improved implementation
}

16. Async/Await

For non-blocking code execution:

using System.Threading.Tasks;

public static async Task DownloadFileAsync(string url, string filePath)
{
// Simulate downloading data asynchronously
await Task.Delay(2000); // Simulate a 2-second download

// Write downloaded data to the file
File.WriteAllText(filePath, “Downloaded content”);
Console.WriteLine($”File downloaded to: {filePath}”);
}

public static void Main(string[] args)
{
string url = “https://example.com/data.txt”;
string filePath = “downloaded_data.txt”;

DownloadFileAsync(url, filePath);

// Continue program execution while download happens in the background
Console.WriteLine(“Downloading file…”);
Console.WriteLine(“Meanwhile, you can do other things…”);
}

17. Miscellaneous

Additional language features:

enum, interface, class, record, struct

dynamic, is, as, var, nameof

18. String Manipulation

Powerful string handling methods:

string.Concat(); // Combine strings
string.Join(); // Join elements
str.Split(); // Split string
str.ToUpper(); // Convert to uppercase
str.ToLower(); // Convert to lowercase

19. File I/O

Operations with files:

using System.IO; // Required for File I/O

File.ReadAllText(path); // Read file content
File.WriteAllText(path, content); // Write to file
File.Exists(path); // Check file existence

20. Date & Time

Date and time manipulation:

using System;

public static void Main(string[] args)
{
DateTime startDate = DateTime.Parse(“2024-03-10”);
DateTime endDate = DateTime.Now;

TimeSpan difference = endDate – startDate;
Console.WriteLine($”Time difference: {difference.Days} days, {difference.Hours} hours”);
}

21. Generics

Type-safe data structures:

public class Stack<T>
{
private List<T> items = new List<T>();

public void Push(T item)
{
items.Add(item);
}

public T Pop()
{
T item = items[items.Count – 1];
items.RemoveAt(items.Count – 1);
return item;
}
}

public static void Main(string[] args)
{
Stack<string> messages = new Stack<string>();
messages.Push(“Hello”);
messages.Push(“World”);

string message = messages.Pop();
Console.WriteLine(message); // Output: World
}

22. Nullables

Allow value types to be null:

int? nullableInt = null; // Nullable integer

23. Attributes & Reflection

Metadata and type introspection:

public class Person
{
public string Name { get; set; }
public int Age { get; set; }
}

public static void Main(string[] args)
{
Type personType = typeof(Person);
PropertyInfo[] properties = personType.GetProperties();

foreach (PropertyInfo property in properties)
{
Console.WriteLine(property.Name); // Output: Name, Age
}
}

24. Extension Methods

Add methods to existing types:

public static class StringExtensions
{
public static string ToUppercase(this string str)
{
return str.ToUpper();
}
}

public static void Main(string[] args)
{
string message = “Hello, world!”;
string uppercased = message.ToUppercase(); // Using the extension method
Console.WriteLine(uppercased); // Output: HELLO, WORLD!
}

25. Dependency Injection

Loosely coupled code design:

public interface ILogger
{
void LogMessage(string message);
}

public class MyService
{
private readonly ILogger _logger;

public MyService(ILogger logger)
{
_logger = logger;
}

public void DoSomething()
{
_logger.LogMessage(“Doing something…”);
}
}

// Implementing the ILogger interface (example)
public class ConsoleLogger : ILogger
{
public void LogMessage(string message)
{
Console.WriteLine(message);
}
}

public static void Main(string[] args)
{
ILogger logger = new ConsoleLogger();
MyService service = new MyService(logger);
service.DoSomething();
}

26. Partial Classes

Splitting a single class definition:

public partial class MyClass { /*…*/ } // Partial class definition

27. Interoperability

Interop with other languages:

using System;
using System.Runtime.InteropServices;

[DllImport(“user32.dll”)]
public static extern int MessageBox(IntPtr hWnd, string lpText, string lpCaption, uint uType);

public static void Main(string[] args)
{
MessageBox(IntPtr.Zero, “Hello from C#!”, “Interop Example”, 0);
}

28. Anonymous Types

Creating unnamed types:csharpCopy code

var person = new { Name = “John”, Age = 30 };
Console.WriteLine($”Name: {person.Name}, Age: {person.Age}”);

29. Tuple

Data structures with a specific number of elements:

(string Name, int Age) person = (“Alice”, 30);
Console.WriteLine($”Name: {person.Name}, Age: {person.Age}”); // Accessing elements using Item1 and Item2

30. Pattern Matching

Simplifies certain programming tasks:

object obj = new Person { Name = “Bob”, Age = 25 };

if (obj is Person { Name: “Bob”, Age >= 18 })
{
Console.WriteLine(“Bob is an adult.”);
}

31. Local Functions

Encapsulate logic within methods:

public static int Calculate(int number)
{
int Factorial(int n)
{
if (n == 0) return 1;
return n * Factorial(n – 1);
}

return Factorial(number);
}

public static void Main(string[] args)
{
int result = Calculate(5);
Console.WriteLine($”5! = {result}”);
}

32. Records

Concise syntax for reference types:

public record Person(string Name, int Age);

public static void Main(string[] args)
{
Person person1 = new Person(“Alice”, 30);
Person person2 = new Person(“Alice”, 30);

// Records provide default equality comparison
if (person1 == person2)
{
Console.WriteLine(“People are equal”);
}
}

33. with Expressions

Non-destructive mutation for records:

var john = new Person(“John”, 30);
var jane = john with { Name = “Jane” }; // Non-destructive mutation

34. Indexers and Ranges

Flexible data access:

int[] arr = {0, 1, 2, 3, 4, 5};
var subset = arr[1..^1]; // Indexer and range usage

35. using Declaration

Dispose of IDisposable objects:

using var reader = new StreamReader(“file.txt”); // using declaration

36. Nullable Reference Types (NRTs)

Avoid null reference exceptions:

public class Person
{
public string Name { get; set; }
public int Age { get; set; }
}

public static void Main(string[] args)
{
Person person = new Person() { Age = 30 };

// NRTs require null checks before accessing properties
if (person?.Name != null)
{
Console.WriteLine(person.Name);
}
else
{
Console.WriteLine(“Name is null”);
}
}

37. Pattern-Based Using

More patterns in the using statement:

public ref struct ResourceWrapper { /*…*/ } // Resource wrapper

using var resource = new ResourceWrapper(); // Pattern-based using

38. Property Patterns

Deconstruct objects in pattern matching:

if (obj is Person { Name: “John”, Age: var age }) { /*…*/ } // Property pattern matching

39. Default Interface Implementations

Interfaces with default method implementations:

public interface IPerson { /*…*/ } // Interface with default method
public class MyClass : IPerson { /*…*/ } // Class implementing interface

40. Dynamic Binding

Runtime type resolution:

dynamic d = 5; // Dynamic binding
d = “Hello”; // No compile-time type checking

Conclusion

This structured C# Cheat Sheet concludes with advanced topics and techniques, providing a comprehensive reference for developers aiming to enhance their C# programming skills. For detailed examples and further exploration, refer to the specific sections outlined in this guide. Happy coding!

Clap if you believe in unicorns & well-structured paragraphs! 🦄📝

Socials: C# Publication | LinkedIn | Instagram | Twitter | Dev.to

Inspired By: https://zerotomastery.io/cheatsheets/csharp-cheat-sheet/#constants

Leave a Reply

Your email address will not be published. Required fields are marked *

Stiri similare