C# Data Types Tutorial and Examples

C# Data Types Tutorial and Examples

A data type is a data representation which determines the following:

  1. How the values of a given type are stored in memory.
  2. The set of values that are stored.
  3. The set of operations that can be applied to all the values in that set.

A data type can also simply be referred to as a type.

Every variable normally has a data type that determines the kind of data that it can hold.

Categories for Data Types

Data types can categorized into two general categories:

  1. Built-in data types - These are data types predefined by the programming language.
  2. User-Defined data types - Custom data types created by the programmer.

Basic Measurement Units of data

Computers can handle as the smallest piece of data a bit.

A bit is a single binary digit of memory that can have either 0 or 1.

A byte is a chunk of memory holding 8 bits. A signed byte can hold from 0 (00000000 in binary) to 255 (11111111 in binary).

Some of the measurement units you may have heard of in computers with regards to space include:

Size Equivalence
1 byte 8 bits
1 Kilobyte 1024 bytes
1 Megabyte 1024 kilobytes
1 Gigabyte 1024 megabytes
1 Terabyte 1024 gigabytes

Multiple bytes get grouped into words that contain 2, 4 or more bytes depending on the computer hardware.

Majority of computers these days use 4-byte(32-bit) words or 8-byte(64-bit) words.

C# also groups bytes in different ways to form data types with a greater logical meaning. E.g it uses 4 bytes to make an integer, a numeric data type that holdvalues between: −2,147,483,648 to 2,147,483,647.

C# defines some keywords for fundamental data types. These can be used to represent:

  • Local variables
  • Class member variables.
  • Return values for methods.
  • Parameters.

Why Data Types?

C# is a strongly typed programming language.

This implies that in C# all operations are type checked at compile time by the compiler for type compatibility.

So if an illegal operation or assignment is detected, then an error is flaged immediately. The error has to be fixed before successful compilation.

Thus this compile-time type checking helps write safe code that is reliable.

However, obviously for us to talk about type checking then it means we need the types, or the data types.

Therefore all variables, expressions and values in C# have types. Having types also helps in determining the operations that can be done on given types.

In C# there are two general categories of data types:

  1. Value Types - Holds an actual value say for example an int value of 45. Int in this case is a value type.
  2. Reference Types - Holds a reference to the value, not the actual value. e.g is the class.

Value Types

Value types hold actual values, single values.

are also called simple types. Or primitive types.

Ther are 13 built in value types in C#. They provide the basis of C#'s type system.

The low level data elements onto which all C# programs rely on.

Using the new Operator with Intrinsic Data Types

All the intrinsic data types support a default constructor.

This allows the creation of variables using the new keyword. This will automatically set the variable to its default value as follows:

  • bool : false
  • Integer : 0
  • Float : 0.0
  • char : single empty character
  • BigInteger : 0
  • DateTime : 1/1/0001 12:00:00 AM
  • Object : null


int age= new int();
float salary=new float();
double d=new double();
bool isMarried=new bool();
DateTime date=new DateTime();

Pre-Defined Data Types

There are 16 predefined types in C#. These types can be divided into:

  1. Simple Types(13)
  2. Non-Simple Types(3)

All these predefined types are in lowercase characters.

The C# predefined types map directly to underlying .NET Base types.

The C# names are the aliases for these .NET base types.

Simple Types

The simple types include:

  1. Numeric Types(11). These include:
    • Integers : Signed and Unsigned.
    • Floating Point Numbers : Floats and Double.
    • Decimal : High precision decimal type.
  2. Unicode Character type - Char.
  3. Boolean : bool represents true or false.
Name Description Range Base Type Default Value
sbyte 8-bit signed integer -128 to 127 System.SByte 0
byte 8-bit unsigned integer 0 to 255 System.Byte 0
short 16-bit signed integer -32,768 to32,767 System.Int16 0
ushort 16-biy unsigned integer 0 to 65,535 System.UInt16 0
int 32-bit signed integer -2,147,483,648 to 2,147,483,647 System.Int32 0
uint 32-bit unsigned integer 0 to 4,294,967,295 System.UInt32 0
long 64-bit signed integer -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 System.Int64 0
ulong 64-bit unsigned integer 0 to 18,446,744,073,709,551,615 System.UInt64 0
float Single precision floating point -1.5e45 to 3.4e38 System.Single 0.0f
double Double precision floating point -5e324 to 1.7e308 System.Double 0.0d
decimal 28-bit significant digit precision decimal ±1.0e28 to ±7.9e28 System.Decimal 0m
bool Boolean value true, false System.Boolean false
char Unicode character U+0000 to U+ffff System.Char x0000

Non-simple Types

The non-simple types include:

  1. string - a seqeunce of unicode characters.
  2. object - base type for creation of all other types.
  3. dynamic - usable when working with assemblies written in dynamic languages.
Name Description Base Type
object base class for all types including simple types System.Object
string sequence of zero or more Unicode characters System.String
dynamic Type designed to be used with assemblies written in dynamic languages No base type

DataType Conversions

Programs are meant to manipulate data. And these data do exist in various types.

Sometimes you need to convert one data type to another.

C# provides us around six ways of converting data from one form to another:

  1. Implicit Conversions.
  2. Data Casting.
  3. Using the as Operator.
  4. Data Parsing.
  5. Using System.Convert.
  6. Using System.BitConverter.

1. Implicit Conversion

Implicit Conversions can be categorized into two

(a). Widening Conversions

Widening conversions occur when a variable of one data type is assigned to a variable of another data type whose maximum capacity is larger than former data type.
This involves storing a value in a variable that is guaranteed to to hold that value.

For example saving an int value to a long varaible.


using System;

namespace DataTypeConversions
class Program
static void Main()
int numOfPeople = 999;
long totalPopulation = numOfPeople;

        Console.WriteLine("numOfPeople is of data type " + numOfPeople.GetType());
        Console.WriteLine("totalPopulation is of data type "+totalPopulation.GetType());



numOfPeople is of data type System.Int32
totalPopulation is of data type System.Int64

You can see that numOfPeople is of type System.Int32, which is actually int while totalPopulation is of type System.Int64 which is the long.

(b). Narrowing Conversions

In contrast in narrowing conversions the source value cannot fit into the destination variable.

For example if you have an int value and you want to convert it into a byte variable.

Well this cannot happen implicitly, even if the value itself is small enough say even 1 to fit into the destination variable.

Let's see an example:

int numOfPeople = 1;
byte enlightenedPeople = numOfPeople; //error won't compile

This cannot happen in C#. We cannot implicitly narrow say an int to a byte. To continue with the narrowing conversion you have to do it explicitly.

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