Introduction to C#

C# is Microsoft's flagship language — modern, type-safe, and the backbone of Azure cloud, ASP.NET APIs, Unity games, and enterprise software across South Africa.

using System;

class Hello {
    static void Main(string[] args) {
        Console.WriteLine("Sawubona, world!");
    }
}

What is C#?

C# (C-sharp) was designed by Anders Hejlsberg at Microsoft, first released in 2000. It is a statically typed, object-oriented language that runs on the .NET runtime (CLR). Like Java, it compiles to intermediate language (IL) that the CLR executes — giving it portability across Windows, Linux, and macOS. Unlike Java, C# has properties, LINQ, async/await, nullable reference types, and records built into the language.

Why C# Matters in South Africa

Microsoft's technology stack — Azure cloud, SQL Server, ASP.NET, SharePoint, Office 365 — is embedded in South African banking, insurance, retail, and government. Absa, Discovery, Standard Bank, and many government departments run on .NET infrastructure. Unity, the dominant game engine, uses C# as its scripting language. Knowing C# opens paths to enterprise backend development, cloud engineering, and game development.

Modern Top-Level Statements

C# 9+ supports top-level statements — for simple programs you can skip the class and Main boilerplate:

// No class or Main needed in C# 9+
Console.WriteLine("Sawubona, world!");
Console.WriteLine("Welcome to Your IT Tutor C# training.");

// String interpolation — prefix with $ and embed {expressions}
string name = "Thandi";
int age = 21;
Console.WriteLine($"Hello, {name}. You are {age} years old.");
Console.WriteLine($"In 5 years: {age + 5}");

C# vs Java — Key Differences to Know

• Method names — PascalCase in C# (GetLength) vs camelCase in Java (getLength).
• Properties — C# has built-in property syntax instead of explicit getters/setters.
• var — compile-time type inference. C# has had it since 2008.
• decimal type — C# has a base-10 decimal type for financial precision (Java relies on BigDecimal).
• LINQ — Language Integrated Query for collections, databases, and XML — no Java equivalent in the language itself.

Practice Task

Common Mistakes

• Forgetting using System; when not using top-level statements — Console is in the System namespace.
• Forgetting the $ prefix on an interpolated string — {name} prints literally.
• camelCase method names — in C#, methods are PascalCase: WriteLine not writeLine.
• Installing Visual Studio without the .NET SDK workload — you need the SDK to compile.