C# Syntax Basics

You now know about classes, the Main() method, statements, and code blocks. Let's summarize a few basic syntax rules that apply to every C# program.

Console.WriteLine("Hello!"); // correct
console.writeline("Hello!"); // Error! C# is case-sensitive

This applies to everything in C#: class names, method names, keywords like "class" or "static". A single letter with the wrong capitalization leads to a compiler error.

Unlike some other languages, C# does not require the file name to match the name of a class inside it — a file can be named anything ending in ".cs". Even so, most C# developers name their file after the main class it contains, purely as a helpful convention.

class Program
{
    static void Main()
    {
        Console.WriteLine("Hello, C#!");
    }
}

C# is case-sensitive (for example, "Main" and "main" are different).

Indentation — meaning spaces at the start of a line that visually shift nested blocks inward — is, on the other hand, not necessary for the compiler. C# compiles code without any indentation just fine. Still, you should always indent cleanly, because it makes your code much easier for people to read.

class Program {
static void Main() {
Console.WriteLine("Hello, C#!");
}
}

Which statement about indentation in C# is correct?

In summary, every C# program follows these rules: the code lives in a class, execution starts in the Main() method, every statement ends with a semicolon, related statements sit in a block of curly braces, and C# is case-sensitive throughout.

In C#, a file containing your code must end with the extension ____.