C# Programming Tutorial: From Fundamentals to Advanced Application Development

📘 Chapter 2: C# Syntax, Variables, and Data Types

🧠 Introduction

Every programming language has its own set of rules—its syntax—that defines how programs are written and interpreted. In this chapter, we explore the foundational elements of C# syntax, including statements, variables, and data types, which are essential to writing any program.

📚 1. C# Syntax Overview

C# syntax is influenced by C, C++, and Java. It's clean, structured, and consistent—great for beginners and professionals alike.

✅ Basic Syntax Elements

✅ Example Program:

using System;

class Hello

{

    static void Main()

    {

        Console.WriteLine("Welcome to C# syntax!");

    }

}

📦 2. Statements and Expressions

• A statement performs an action (e.g., assignment, method call).
• An expression evaluates to a value (e.g., x + y, 10 * 2).

int x = 5;        // statement with expression

Console.WriteLine(x + 2);  // expression in output

🧾 3. Variables in C#

A variable is a name given to a memory location to store data. It can be changed during program execution.

✅ Syntax:

dataType variableName = value;

📋 Variable Declaration Examples

🧠 Variable Naming Rules

1. Must start with a letter or underscore
2. Cannot start with a digit
3. Cannot use C# keywords
4. Case-sensitive (Name ≠ name)
5. Meaningful names are preferred

🔢 4. C# Data Types

C# is a strongly-typed language—every variable must have a declared type.

🔹 Categories of Data Types

🔹 Value Types

Stored directly in memory and hold data.

🔹 Reference Types

They refer to memory addresses and store a reference, not the data itself.

✅ Example: Value vs Reference

int x = 10;

string name = "John";

• x holds the number 10.
• name refers to a string stored elsewhere.

🧠 5. Constants and Readonly

🔹 Constant (const)

A compile-time constant that cannot be changed after it's declared.

const double Pi = 3.14159;

🔹 Readonly

Can be assigned at declaration or in constructor, but not modified later.

readonly int id;

🔁 6. Type Conversion in C#

C# supports both implicit and explicit type conversion.

✅ Implicit Conversion

Safe conversions (e.g., int to float):

int a = 10;

float b = a;

✅ Explicit Conversion (Casting)

Risky conversions that require a cast:

double x = 10.5;

int y = (int)x;  // y = 10

🔹 Using Convert Class

string s = "123";

int num = Convert.ToInt32(s);

📋 Type Conversion Table

📌 7. Variable Scope in C#

Scope determines the accessibility and lifetime of a variable.

✅ Example:

class Test {

    int age = 30;  // instance variable

    void Show() {

        int x = 5;  // local variable

        Console.WriteLine(x + age);

    }

}

🧪 Sample Program: Type Conversion and Variables

using System;

class Program

{

    static void Main()

    {

        int a = 20;

        double b = a; // implicit

        double c = 12.9;

        int d = (int)c; // explicit

        Console.WriteLine("b = " + b); // 20

        Console.WriteLine("d = " + d); // 12

    }

}

🧠 Real-World Usage

✅ Summary Table