C#

Here's a cheat sheet summarizing some of the key concepts, syntax, and features of the C# programming language:

csharp

// C# Language Cheat Sheet

// Comments: Single-line comment

/*
   Multi-line
   comment
*/

// Data Types:
int          // Integer
float        // Floating-point number
double       // Double precision floating-point number
char         // Character
bool         // Boolean
string       // String
decimal      // Decimal number
DateTime     // Date and time
var          // Implicitly typed variable

// Variables:
int age = 25;          // Variable declaration and initialization
float pi = 3.14;
char letter = 'A';

// Constants:
const int MAX_VALUE = 100;   // Constant declaration

// Input and Output:
Console.WriteLine("Hello, World!");   // Output to console
int age = Convert.ToInt32(Console.ReadLine());   // Input from user

// Arithmetic Operators:
+, -, *, /, %        // Addition, Subtraction, Multiplication, Division, Modulo

// Relational Operators:
==, !=, >, <, >=, <=   // Equal to, Not equal to, Greater than, Less than, Greater than or equal to, Less than or equal to

// Logical Operators:
&&   // Logical AND
||   // Logical OR
!    // Logical NOT

// Control Flow:
if (condition) {
    // Code executed if condition is true
}
else if (condition2) {
    // Code executed if condition2 is true
}
else {
    // Code executed if no previous conditions are true
}

switch (variable) {
    case value1:
        // Code executed if variable is equal to value1
        break;
    case value2:
        // Code executed if variable is equal to value2
        break;
    default:
        // Code executed if no previous cases match
}

while (condition) {
    // Code executed repeatedly while condition is true
}

for (initialization; condition; increment/decrement) {
    // Code executed repeatedly until condition is false
}

// Functions:
return_type function_name(parameter1, parameter2) {
    // Code executed by the function
    return value;   // Optional return statement
}

// Classes and Objects:
class MyClass {
    private int x;
    public void SetX(int value) {
        x = value;
    }
    public int GetX() {
        return x;
    }
}

MyClass obj = new MyClass();       // Object instantiation
obj.SetX(5);                       // Accessing member functions
int value = obj.GetX();

// Inheritance:
class DerivedClass : BaseClass {
    // Derived class definition
}

// Interfaces:
interface IMyInterface {
    void MyMethod();
}

class MyClass : IMyInterface {
    public void MyMethod() {
        // Method implementation
    }
}

// Properties:
public int MyProperty { get; set; }    // Automatic property

// Exception Handling:
try {
    // Code that may throw an exception
}
catch (ExceptionType e) {
    // Code to handle the exception
}
finally {
    // Code that always executes, regardless of whether an exception is thrown
}

// Generics:
class MyClass<T> {
    T MyMethod(T parameter) {
        // Method implementation
        return parameter;
    }
}

// LINQ (Language-Integrated Query):
var result = from variable in collection
             where condition
             select variable;

// Collections (e.g., Lists, Arrays, Dictionaries, etc.):
List<int> numbers = new List<int>();             // List declaration
int[] array = new int[5];                         // Array declaration
Dictionary<string, int> dict = new Dictionary<string, int>();   // Dictionary declaration

This cheat sheet covers some of the most commonly used features and syntax in the C# programming language. It serves as a handy reference for quick look-ups and reminders while programming in C#.