C# Basics for Beginners

C# (pronounced "C-sharp") is the most popular language on the .NET platform. It is a statically typed, object-oriented language that reads cleanly and gives helpful compiler errors, which makes it a great first language. This guide covers the absolute basics: how a program is structured, how to declare variables, how to read input and print output, and how to make decisions with if and loops. All examples target modern .NET (C# 14).

A minimal C# program

Modern C# supports top-level statements, so a tiny program needs no class or Main method:

// Program.cs
// Console.WriteLine prints a line of text to the terminal.
Console.WriteLine("Welcome to C#!");

Run it with dotnet run. Every C# statement ends with a semicolon ;.

Variables and types

A variable is a named box that holds a value. C# is statically typed, meaning each variable has a type fixed at compile time:

int age = 19;            // whole number
double marks = 84.5;     // number with a decimal point
string city = "Jalgaon"; // text
bool isEnrolled = true;  // true or false

// 'var' lets the compiler infer the type from the value on the right.
var greeting = "Hi";     // compiler knows this is a string

Console.WriteLine(age);      // 19
Console.WriteLine(greeting); // Hi

var is just a shortcut — the type is still fixed once assigned. You cannot later put a number into a string variable.

Output and input

Use Console.WriteLine to print and Console.ReadLine to read a line the user types:

Console.Write("Enter your name: ");   // Write (no new line) keeps the cursor on the same line
string? name = Console.ReadLine();    // ReadLine returns the text the user typed (may be null)

// String interpolation: the value of 'name' is placed inside the text.
Console.WriteLine($"Hello, {name}!");

Console.ReadLine always returns text. To get a number you must convert it:

Console.Write("Enter your age: ");
string? input = Console.ReadLine();
int age = int.Parse(input!);          // convert text "20" into the number 20
Console.WriteLine($"Next year you'll be {age + 1}.");

For safer conversion that won't crash on bad input, use int.TryParse (covered in the data-types article).

Operators

int a = 10, b = 3;
Console.WriteLine(a + b);  // 13  addition
Console.WriteLine(a - b);  // 7   subtraction
Console.WriteLine(a * b);  // 30  multiplication
Console.WriteLine(a / b);  // 3   integer division (drops the remainder)
Console.WriteLine(a % b);  // 1   modulus (the remainder)

Note that 10 / 3 gives 3, not 3.33, because both numbers are integers. Use double for decimal division.

Making decisions and looping

int score = 72;

// if / else if / else chooses one branch to run.
if (score >= 75)
    Console.WriteLine("Distinction");
else if (score >= 40)
    Console.WriteLine("Pass");
else
    Console.WriteLine("Try again");

// A for loop repeats a block a known number of times.
for (int i = 1; i <= 3; i++)
{
    Console.WriteLine($"Attempt {i}");
}
// Output: Attempt 1 / Attempt 2 / Attempt 3

The == operator checks equality, while = assigns a value — a classic beginner trap.

Common mistakes

• Using = instead of == in conditions. if (x = 5) is wrong; use if (x == 5). C# will usually catch this for bool, but the habit matters.
• Forgetting the semicolon. Every statement ends with ;. Missing one is the most common compile error.
• Treating Console.ReadLine output as a number. It is always text; convert it with int.Parse or int.TryParse.
• Integer division surprise. 5 / 2 is 2, not 2.5. Make at least one operand a double.
• C# is case-sensitive. Name and name are different variables.

FAQ

Is C# the same as C or C++? No. They share some syntax, but C# is a higher-level, memory-managed language that runs on .NET.

Do I need to memorize all the types? No — start with int, double, string, and bool. The rest come naturally.

Keep learning

• Hub: Learn .NET
• Next: C# Data Types & Variables
• Related: What is .NET?

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