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Elmer Chacon
Elmer Chacon

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🧠 The Ultimate C# Cheat Sheet & Quick Reference

#csharp #programming #productivity #developer

Whether you're new to C# or a seasoned developer who needs a quick refresher, this cheat sheet is for you. It’s a compact but powerful reference filled with practical examples and syntax reminders that’ll keep you sharp and efficient as you code.

🧱 Basics

✅ Variables

int age = 30;
double pi = 3.14;
string name = "Elmer";
bool isActive = true;
char initial = 'E';
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✅ Constants

const double Gravity = 9.81;
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✅ Nullable types

int? score = null;
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🔁 Conditionals & Loops

✅ If-Else

if (age > 18)
    Console.WriteLine("Adult");
else
    Console.WriteLine("Minor");
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✅ Switch

switch (dayOfWeek)
{
    case "Monday":
        Console.WriteLine("Start of week");
        break;
    default:
        Console.WriteLine("Any day");
        break;
}
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✅ For loop

for (int i = 0; i < 5; i++)
    Console.WriteLine(i);
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✅ Foreach

string[] fruits = { "Apple", "Banana" };
foreach (string fruit in fruits)
    Console.WriteLine(fruit);
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✅ While

int counter = 0;
while (counter < 3)
{
    Console.WriteLine(counter);
    counter++;
}
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📦 Classes & Objects

✅ Defining a Class

public class Dog
{
    public string Name { get; set; }
    public void Bark() => Console.WriteLine("Woof!");
}
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✅ Using a Class

var myDog = new Dog { Name = "Rex" };
myDog.Bark();
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🎯 Methods

✅ Method with Parameters and Return

int Add(int a, int b) => a + b;
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✅ Optional Parameters

void Print(string msg = "Hello") => Console.WriteLine(msg);
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🧰 Collections

✅ Arrays

int[] nums = { 1, 2, 3 };
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✅ List

List<string> names = new List<string> { "Alice", "Bob" };
names.Add("Charlie");
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✅ Dictionary

var ages = new Dictionary<string, int> { { "Tom", 30 } };
Console.WriteLine(ages["Tom"]);
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🚀 LINQ 

var evens = numbers.Where(n => n % 2 == 0).ToList();
var names = users.Select(u => u.Name).ToList();
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⚙️ Exception Handling 

try
{
    int x = 10 / 0;
}
catch (DivideByZeroException ex)
{
    Console.WriteLine("Cannot divide by zero");
}
finally
{
    Console.WriteLine("Cleanup code");
}
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🔄 Async / Await 

async Task<string> GetDataAsync()
{
    await Task.Delay(1000);
    return "Data loaded";
}
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🛠️ Useful Tips

  • Use var when the type is obvious

  • Use ?? for null-coalescing:

string name = input ?? "Default";
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  • Use string interpolation: 
Console.WriteLine($"Hello, {name}!");
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📌 Bonus: Attributes & Enums

✅ Enum

enum Status { Pending, Approved, Rejected }
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✅ Attribute

[Obsolete("Use NewMethod instead")]
void OldMethod() {}
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🧠 Final Thoughts

This cheat sheet is just the tip of the iceberg when it comes to C#. Keep it handy as a quick reference, especially when you're juggling multiple projects or switching between languages. C# is expressive, powerful, and clean—and with a reference like this, you can focus more on building and less on remembering syntax.

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