The Essential C# Cheat Sheet: Core Syntax and Constructs for Rapid Development
In the world of coding, C# stands tall as a go-to language for building everything from big company apps to fun games in Unity. Developers love it for its clean code and strong ties to tools like Azure for cloud work. This cheat sheet cuts through the noise, giving you quick hits on key syntax to speed up your projects without digging through docs.
You get a tight guide here on the basics that matter most. It skips the fluff and focuses on what you use every day. Whether you're new to C# or just need a fast refresh, these tips will save you hours and boost your flow right away.
Section 1: Variables, Data Types, and Operators
Declaring Variables and Understanding Types
C# lets you declare variables with types like int for whole numbers, double for decimals, bool for true or false, string for text, and char for single letters. Use the var keyword to let the compiler guess the type, like var score = 100; it becomes an int automatically. Value types store data directly, while reference types point to data in memory—think int as value and string as reference.
Pick int for most counts since it handles numbers up to about two billion. Go for long if you need bigger ranges, like in data apps, but it takes more space. Short works for small numbers to save memory in tight spots.
- int: 32-bit, -2^31 to 2^31-1
- long: 64-bit, much larger range
- short: 16-bit, for tiny values
This choice matters in games where memory counts.
String Manipulation Fundamentals
Strings in C# handle text with ease. Concatenate them using + , like name = "Hello" + " World";. For cleaner code, try interpolation with $"" : Console.WriteLine($"Hi, {name}!"); it plugs in values smoothly.
Common methods include .Length to get character count, .ToUpper() to make all caps, and .Substring(0, 5) to grab part of the text. Verbatim strings with @"" keep things like paths intact, as in string path = @"C:\MyFolder"; no escape hassles.
In logging, interpolation shines. Say you track user actions: string log = $"{DateTime.Now}: User {userId} logged in."; It makes output clear and quick to build.
Arithmetic, Comparison, and Logical Operators
Basic math uses + for add, - for subtract, * for multiply, / for divide, and % for remainder. Assignment shortcuts like += add and assign, as in total += 5;.
Comparisons check equals with == , greater than > , or not equal != . Logical ops tie them: && for and, || for or, ! for not. So, if (age > 18 && approved) works for checks.
Watch order in big expressions—parentheses help, like (a + b) * c to group first. This avoids bugs in conditions. Always test complex ones step by step.
Section 2: Control Flow Structures
Conditional Statements: If, Else If, and Switch
If statements check conditions simply: if (x > 0) { Console.WriteLine("Positive"); } else { Console.WriteLine("Not positive"); }. Add else if for more options, like if (grade >= 90) { "A"; } else if (grade >= 80) { "B"; }.
Switch beats long if chains for exact matches. Use it on enums or strings: switch (day) { case DayOfWeek.Monday: result = "Start week"; break; default: "Other day"; }. In C# 8 and up, switch expressions return values: string msg = day switch { DayOfWeek.Friday => "Weekend soon!", _ => "Keep going" };.
Picture a menu app. You switch on user choice to pick actions, making code neat and fast to read.
Looping Constructs: For, While, and Do-While
For loops fit when you know the count: for (int i = 0; i < 10; i++) { sum += i; }. It runs init, check, then increment each time.
While waits on a condition: int count = 0; while (count < 5) { count++; }. Do-while runs once first: do { action(); } while (condition); good for menus needing at least one try.
Use break to exit early, like in a search loop when found. Continue skips to next iteration. They keep loops clean without extra flags.
Iterating Collections: Foreach Loops
Foreach shines for lists or arrays: foreach (var item in numbers) { Console.WriteLine(item); }. It reads each without index hassle, ideal for IEnumerable types.
You can read but not change the collection size during loop—add a copy if needed. For mods, use a for loop instead.
In data tasks, foreach processes rows fast. Tip: Stick to in for simple reads; ref helps if tweaking values, but keep it basic for speed.
Section 3: Methods and Functions
Defining and Calling Methods
Methods start with access like public, then return type, name, and params: public int Add(int a, int b) { return a + b; }. Call it as result = Add(3, 4);.
Params pass by value unless ref or out. Value copies data; ref shares changes.
Name methods in PascalCase, like CalculateTotal. It matches C# style for easy team work.
Handling Optional and Output Parameters
Optional params use defaults: public void Print(string msg, bool loud = false) { if (loud) msg = msg.ToUpper(); Console.WriteLine(msg); }. Call with one arg: Print("Hi"); it uses false.
Out params return extras: public bool TryGetValue(int id, out string name) { name = "Found"; return true; }. Like int.TryParse("123", out int num);.
In parsing files, out grabs results without extra objects. It cuts code lines nicely.
Method Overloading and Recursion Overview
Overload by same name, different params: void Greet() { } and void Greet(string name) { }. Compiler picks based on call.
Recursion calls itself, like factorial: int Fact(int n) { if (n <= 1) return 1; return n * Fact(n-1); }. Always set base case to stop.
Use overloads for flexible APIs. Recursion fits trees but watch stack depth.
Section 4: Collections and Arrays
Working with Arrays
Arrays hold fixed sizes: int[] scores = new int[5]; or int[] nums = {1, 2, 3};. Access with scores[0] = 10;.
Sort with Array.Sort(scores); or find length via .Length.
New int[10] makes empty slots; {1,2,3} fills right away. Use arrays for quick, set-size data like coords.
Utilizing Generic Lists (List)
List
Insert at spot: items.Insert(0, 10); but watch shifts.
Lists grow easy, unlike arrays. Removing from front slows it—use Queue for that often.
Dictionaries for Key-Value Mapping
Dictionary<string, int> ages = new Dictionary<string, int>(); ages["Alice"] = 30; get with ages["Alice"].
Check keys: if (ages.ContainsKey("Bob")) { } .Remove("Alice"); clears.
Dictionaries use hash for fast lookups, often in one step. Great for configs or caches.
Section 5: Object-Oriented Programming (OOP) Basics
Classes, Objects, and Constructors
Class Person { public string Name; } then Person p = new Person(); p.Name = "Bob";.
Constructor sets up: public Person(string name) { Name = name; }. This makes new Person("Bob"); ready.
Use this.Name = name; to differ from param. Init lists chain: public Person(string n) : this() { Name = n; } for shared setup.
Properties vs. Fields
Fields hold data private: private string _name;. Properties wrap: public string Name { get { return _name; } set { _name = value; } }.
Auto props simplify: public string Name { get; set; }. Add logic: set { if (value.Length > 0) _name = value; }.
In a bank app, props check balances before set. It hides fields safely.
Inheritance and Abstraction (Interfaces)
Inherit with : class Employee : Person { }. Add methods there.
Interfaces define rules: interface IShape { double Area(); }. class Circle : IShape { public double Area() { return Math.PI * r * r; } }.
Use virtual in base: public virtual void Work() { }. Override in child: public override void Work() { base.Work(); extra(); }.
Interfaces fit multiple types; classes for shared code.
Conclusion: Mastering C# Syntax Speed
This guide covers key C# basics: from variables and operators to loops, methods, collections, and OOP starts. You now have syntax snippets for quick use in daily code.
Apply these right away in your next project—they stick best in action. Build a small app or tweak old code to lock in the patterns. Your C# skills will grow fast with this foundation.
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