https://github.com/ssukhpinder/csharp-cheatsheet
C#: From Fundamentals to Advanced Techniques — A Comprehensive Cheat Sheet
https://github.com/ssukhpinder/csharp-cheatsheet
aspnet aspnetcore coding csharp dotnet dotnet-core microsoft programming
Last synced: 3 days ago
JSON representation
C#: From Fundamentals to Advanced Techniques — A Comprehensive Cheat Sheet
- Host: GitHub
- URL: https://github.com/ssukhpinder/csharp-cheatsheet
- Owner: ssukhpinder
- Created: 2024-03-18T06:10:31.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-03-18T06:12:51.000Z (over 1 year ago)
- Last Synced: 2025-02-28T22:52:14.801Z (8 months ago)
- Topics: aspnet, aspnetcore, coding, csharp, dotnet, dotnet-core, microsoft, programming
- Homepage: https://medium.com/c-sharp-progarmming
- Size: 7.81 KB
- Stars: 5
- Watchers: 1
- Forks: 3
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- Funding: .github/FUNDING.yml
Awesome Lists containing this project
README
The comprehensive C# Cheat Sheet is designed to aid developers in mastering key syntax and concepts related to C# programming.
## Contents
1. Basic Structure
2. Data Types
3. Variables
4. Constants
5. Conditional Statements
6. Loops
7. Arrays
8. Lists
9. Dictionaries
10. Methods
11. Classes & Objects
12. Exception Handling
13. Delegates, Events & Lambdas
14. LINQ (Language-Integrated Query)
15. Attributes
16. Async/Await
17. Miscellaneous
18. String Manipulation
19. File I/O
20. Date & Time
21. Generics
22. Nullables
23. Attributes & Reflection
24. Extension Methods
25. Dependency Injection
26. Partial Classes
27. Interoperability
28. Anonymous Types
29. Tuples
30. Pattern Matching
31. Local Functions
32. Records
33. with Expressions
34. Indexers and Ranges
35. using Declaration
36. Nullable Reference Types (NRTs)
37. Pattern-Based Using
38. Property Patterns
39. Default Interface Implementations
40. 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 numbers = new List();
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 phonebook = new Dictionary();
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 people = new List()
{
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 numbers = new List() { 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
{
private List items = new List();
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 messages = new Stack();
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](https://medium.com/c-sharp-progarmming) | [LinkedIn](https://www.linkedin.com/in/sukhpinder-singh-532284a2/) | [Instagram](https://www.instagram.com/sukhpindersukh/) | [Twitter](https://twitter.com/sukhsukhpinder) | [Dev.to](https://dev.to/ssukhpinder)
**Inspired By:** [https://zerotomastery.io/cheatsheets/csharp-cheat-sheet/#constants](https://zerotomastery.io/cheatsheets/csharp-cheat-sheet/#constants)