📦 C# Data Types – Understanding Built-in and Custom Types

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🧲 Introduction – Why Data Types Matter in C#

Every piece of data in C# has a data type that determines how much memory it takes, how it’s stored, and what operations can be performed on it. Understanding C# data types is essential for writing type-safe, efficient, and error-free code.

🎯 In this guide, you’ll learn:

• The main categories of data types in C#
• Differences between value types and reference types
• How to use and declare each type
• Common pitfalls and best practices

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🔍 Core Concept – What Are C# Data Types?

A data type defines the kind of data a variable can store. C# supports a variety of built-in types and also allows the creation of custom types using classes, structs, and enums.

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📚 Categories of C# Data Types

Category	Examples	Notes
Value Types	int, float, bool, char	Stored on the stack
Reference Types	string, arrays, classes, objects	Stored on the heap
Nullable Types	int?, bool?	Value types that can be null
User-defined Types	class, struct, enum, interface	Built by developers

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🔢 Built-in Value Types

Type	Size	Example	Description
int	4 bytes	int age = 30;	Integer (whole number)
float	4 bytes	float pi = 3.14f;	Single-precision decimal
double	8 bytes	double e = 2.718;	Double-precision decimal
char	2 bytes	char grade = 'A';	Single character
bool	1 byte	bool isValid = true;	Boolean true/false

📘 Best Practice: Use double for precision math and int for counters or indexes.

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🔠 Reference Types

Type	Description
string	Sequence of characters
object	Base type of all types in .NET
Arrays	Fixed-size collections like int[] numbers
Class	Custom reference type

🧠 Note: Reference types store a pointer to the memory location.

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💻 Code Example – Using Different Data Types

using System;

class DataTypeDemo
{
    static void Main()
    {
        int age = 28;
        double salary = 55000.75;
        char grade = 'A';
        bool isEmployed = true;
        string name = "John";

        Console.WriteLine($"Name: {name}, Age: {age}, Grade: {grade}, Salary: {salary}, Employed: {isEmployed}");
    }
}

📤 Output:

Name: John, Age: 28, Grade: A, Salary: 55000.75, Employed: True

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🧠 Value Types vs Reference Types

Feature	Value Type	Reference Type
Memory Location	Stack	Heap
Default Behavior	Copy by value	Copy by reference
Null Assignment	Not allowed (unless nullable)	Allowed
Performance	Faster for small data	Efficient for large/complex data

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💡 Tips, Pitfalls & Best Practices

💡 Tip: Use var when the type is obvious, but avoid overusing it.

📘 Best Practice: Choose the right type based on the required precision and memory needs.

⚠️ Pitfall: Using float or double for money calculations may lead to rounding errors—use decimal instead.

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🛠️ Use Cases – Where Data Types Are Used

• int, double for calculations and counters
• string for user input, messages, file names
• bool for toggles, status flags
• char for character data (e.g., grades, initials)
• Custom classes/structs for structured data

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📌 Summary – Recap & Next Steps

C# provides a rich set of data types for efficient and flexible data storage. Knowing which type to use helps you write cleaner, faster, and safer code.

🔍 Key Takeaways:

• Value types are stored on the stack; reference types on the heap
• Use decimal for money, string for text, and bool for logic
• Understand how types affect performance and memory

⚙️ Coming up: Learn how to safely convert between types using 📦 C# Type Casting / Type Conversion

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❓ FAQ – C# Data Types

❓ What are the main data types in C#?
✅ C# includes value types (e.g., int, float) and reference types (e.g., string, object, arrays).

❓ What is the default value of a C# data type?
✅ For value types: 0 for numbers, false for bool, '\0' for char. For reference types: null.

❓ What type should I use for currency?
✅ Use decimal for high-precision financial calculations.

❓ Can I create my own data types in C#?
✅ Yes. You can define custom classes, structs, enums, and interfaces.

❓ What is the base type of all C# types?
✅ The object type is the base class for all types in C#.

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