C# Basic Data Types

In C#, data is stored using different types, and each data type defines how much memory is used and which operations can be performed. These types play a key role in how a program behaves. In this article, we will explore numeric, textual, logical, dynamic, and nullable data types with practical examples.

Choosing the right data type is a crucial part of learning C#. Proper type selection improves performance, optimizes memory usage, and helps prevent common programming errors. Understanding the fundamental data types early on provides a solid foundation for building reliable applications.

Numeric Types

Numeric types are used for integers and floating-point numbers. For financial calculations, decimal is recommended.

int age = 25;
double pi = 3.14159;
decimal price = 19.99m;

Console.WriteLine(age);
Console.WriteLine(pi);
Console.WriteLine(price);

Text Types

char holds a single character, while string holds a sequence of characters.

char firstLetter = 'M';
string message = "Hello";

Console.WriteLine(firstLetter);
Console.WriteLine(message);

Logical Type

bool can only hold true or false. It is widely used in conditions.

bool isStudent = true;
bool isGraduate = false;

Console.WriteLine(isStudent);
Console.WriteLine(isGraduate);

Object and Dynamic Types

object, var, and dynamic are used for flexible usage.

object data = 42;
var text = "Hello";
dynamic variable = 5;
variable = "Now it's a string";

Console.WriteLine(data);
Console.WriteLine(text);
Console.WriteLine(variable);

Nullable Types

Value types (e.g. int, double, bool) cannot be null by default. Adding ? allows them to be nullable.

int? grade = null;

if (grade == null)
    Console.WriteLine("No grade entered.");
else
    Console.WriteLine($"Grade: {grade}");

When Should Each Data Type Be Used?

• int: Counters, age values, quantities, and whole numbers
• double: Physical measurements and approximate calculations
• decimal: Monetary values, prices, and financial calculations
• string: Text input received from the user
• bool: Conditions, comparisons, and control flow logic

Assignments Between Data Types and Type Conversions

In C#, variables of different data types cannot always be assigned to each other directly. Attempting to assign incompatible types results in a compile-time error.

Invalid Assignments

int number = 10;
string text = number; // ERROR

bool flag = true;
int value = flag;     // ERROR

In the examples above, the assignments fail because the data types are not compatible.

In the image above, Visual Studio immediately detects invalid assignments between incompatible data types. The example shows attempts to assign values between types such as bool and int, which are not directly compatible. The editor highlights the issue with a red underline and displays a compile-time error like CS0029.

Implicit Conversions

int small = 5;
double large = small; // Valid

Smaller numeric types can be automatically converted to larger numeric types.

Explicit Conversions

double pi = 3.14;
int wholeNumber = (int)pi; // 3

Conversions that may cause data loss or precision loss require explicit casting.

Summary

• Numbers: int, double, decimal
• Text: char, string
• Logical: bool
• Flexible: object, var, dynamic
• Nullable: with ?